WHEN DIANA Kennedy -- cooking teacher, author of three Mexican cookbooks, experimenter in ecological living -- left her home in Mexico for a few days in Washington recently, she spent her time just as you would expect: She demonstrated Mexican cooking and she cooked for her friends. Her visit also included, as anyone who knows this energetic and constantly curious woman would predict, several unexpected events: She received the announcement of being awarded the Mexican government's highest honor, the Aztec Eagle, for having written "the best cookbooks ever in Mexico." She found a new source for the Mexican herb epazote -- in the cracks in the sidewalks of Georgetown. And she solved a mystery.

The mystery began when Pepe Montesinos, owner of Enriqueta's restaurant in Georgetown, read in Kennedy's "Recipes From the Regional Cooks of Mexico," the story of her trip to the Oaxacan village of Tepzuitlan for a barbecue. That just didn't sound right to Montesinos; as far as he knew, only his Oaxacan village, Tezoatlan, made llique, the corn soup she described as accompanying the barbecue. And her description of Tepzuitlan sounded exactly like his village. He pored over his map, quizzed his friends and relatives, even called a telephone operator in Mexico, who confirmed that there was no village in Oaxaca named Tepzuitlan.

That was a couple of years ago. In the meantime, Kennedy was finally persuaded to lunch at Enriqueta's. The last thing a Mexican cookbook writer wants to do on a visit to the United States is to eat in a Mexican restaurant, but Kennedy's irrepressible curiosity won over her reluctance when she heard Enriqueta's was an authentic Mexican rather than Tex-Mex restaurant. She would be interested in trying Enriqueta's after all.

As long as it was off the record.

She did not want the restaurant mentioned, nor her opinion of it; nor did she want to be introduced in the restaurant. After all, she said, she was not a restaurant critic and did not want to be advising a restaurateur how to cook. Too presumptuous.

Enriqueta's was nearly empty just before noon on a Saturday. Kennedy was, as usual, wearing the colors of a Mexican kitchen -- terra cotta, cocoa -- and a soft, woolly hat. She wasn't even hungry and didn't really want to eat, but one must try the guacamole and the refried beans, an enchilada of some sort, maybe one of the stuffed peppers and a mole dish. The menu, she declared, was too long, but it did have some interesting dishes on it.

She tasted the tortilla chips -- something you would never see in Mexico, she pronounced -- with the fresh tomato sauce for dipping. Surprisinglly good, that sauce, with fresh tomatoes and cilantro (coriander). Kennedy brightened. Yes, a very nice little sauce, even if it did need more cilantro.

Montesinos arrived and, already knowing the reporter, seated himself at the table and started to talk about the new dishes he was adding to the menu. The reporter mumbled an introduction, but Montesinos was too preoccupied to notice that the guest's name hadn't been mentioned.

Don't stop with the lunch menu, he insisted, jumping up to bring a dinner menu. He also brought a plate of dried peppers to show what the kitchen had available.

Kennedy couldn't resist. Montesinos would start to tell of an unusual dish he wanted to add to the menu, and she would complete the description. He would talk about the regional origin of a recipe, and she would define it down to the village. She was trying not to be intrusive, but she could not hide the fact that she was knowledgeable. Whatever dish Montesinos mentioned, Kennedy knew all its variations and probably even which side of the road it came from. It was the game of "whom do we know in common," but it was played over foods: Do you know the stew made from that kind of shoot from the plant that grows wild on the third tallest mountain in the region of X? Yes, but I like even better the one from the second tallest mountain, that is made only in the third week of April. Oh, that was my aunt's favorite dish, and I ate it every spring since I was 3.

It was a reporter's nightmare. Not only had the conversation switched almost entirely to Spanish -- which the reporter imperfectly understood, to put it mildly -- but since the entire event was off the record, there was no chance to take notes (or to ask questions that might provide an on-the-record story). It was, however, an absorbing encounter in any language.

Montesinos moved into the "you must try" phase, dashing back and forth to the kitchen to bring another and another dish for Kennedy to taste. Kennedy, whose lack of hunger had been forgotten, could not resist examining, dissecting, tasting, exploring every dish. Montesinos would bring dried peppers, and a heavy-duty pepper discussion would follow. Montesinos would bring a cone of dark, coarse brown sugar -- made by his family on his ranch -- and the various regional names, and shapes, of molded brown sugar would dominate the conversation. Chocolate and vanilla were discussed at length; banana leaves and maguey leaves and avocado leaves became a seminar topic.

Gradually, Montesinos' whole clan was brought into the conversation, the aunt who taught him this dish, the brother who had advised him not to freeze pomegranate seeds -- which Kennedy suggested he try anyway. Both became more animated, Montesinos pulling his chair closer and poking with his finger to prove a point, Kennedy's strong hands expressing nuances of peeling and pounding and shaping.

All this was fueled by food, dish after dish. First the black bean soup with cream: Kennedy has recipes in her books which she considers better than his too-creamy, insufficiently beany version. Montesinos took the criticism well, admitting that he preferred his menu's more classic black bean soup, but the customers preferred the creamy one. He cemented the relationship with a sauce made of dark red chilies that had been charred properly -- a vital point on which they both agreed. That sauce led to talk of pit barbecues, which Montesinos would love to serve if regulations did not forbid his digging a pit in the earth of Georgetown. Talk sidetraced to tortillas; his should be thicker, said Kennedy. Montesinos agreed but explained that it was uneconomical to form them by hand for the restaurant, and regulations prevented him from using the imported tortilla press he had upstairs. On they went, to stuffed chilies, which Kennedy applauded for being stuffed with shredded rather than ground meat and for the chilies being the proper sort, but criticized for the texture of their batter and for the oil in which they were fried.

Montesinos brought a tortilla soup, and after one taste Kennedy had suggestions for improving it, but confided to the reporter that she was not going to tell Montesinos because she was afraid she was afraid she was hurting his feelings. That resolve disappeared under Montesinos' questions. Ten minutes of soup talk -- in Spanish, of course. Far from discouraging Montesinos, it livened him, sent him back for more: lamb wrapped in banana leaves with three sauces. Pork stew with three kinds of peppers. Don't brown the meat, Kennedy suggested, since that dries it and prevents the flavors from penetrating; and next time, try country spareribs instead of the cut of pork that was used.

By now it was obvious to Montesinos that this softspoken but outspoken woman knew Mexico as well as he knew his kitchen. They were two-hour-old friends who shared a consuming interest but had not shared their names with each other.

Then Montesinos caught sight of Kennedy as she turned her head a certain way, and exclaimed, "Are you Diana Kennedy?" Her hat had disguised her just slightly from the photograph on the back of her first book, "The Cuisines of Mexico," a dog-eared copy of which he produced for her to autograph.

The story had not ended. The detective's wrapup was to come. Montesinos accused Kennedy of having invented the name of Tepzuitlan in her barbecue anecdote. "I am found out," she confessed, taken aback that somebody in Washington had caught her having made up the name of a single tiny village in Oaxaca, in order to protect a cook's identity. She explained that she had done it because the anecdote told of her friend's husband getting drunk at the party. Montesinos was fairly leaping with the excitement of Kennedy having written of what he kept calling "my small village." And then it dawned on him. The friend's name was a fake, too. That was his cousin. She had written about his cousin. Kennedy's excitement matched his own, as they exchanged information on how the family was doing these days, and Kennedy promised to bring the cousin news of the family when she delivered the coffee bushes she had promised her.

They ended lunch with handshakes and warm exchanges. Montesinos bringing Kennedy small souvenirs and insisting she must come to his farm in Mexico for wild boar.

Kennedy left with a reporter carrying an empty notebook.

"You might as well write about that, after all," Kennedy volunteered. "Being the widow of a newspaperman, I couldn't have you miss a good story." SIKIL-P'AK (Pumpkin-Seed Dip) (Makes 1 1/2 cups) 1 1/4 cups pumpkin or squash seeds, raw and unhulled 1 chile habanero or any fresh, hot green chili 2 medium tomatoes, about 12 ounces 1 1/2 teaspoons salt, or to taste 2 heaping tablespoons coriander leaves, chopped 2 heaping tablespoons chives, chopped

Heat a frying pan and toast the seeds, turning them constantly, until the hulls are well-browned and crisp (some types of seeds will start to pop open). Set them aside to cool. Meanwhile, toast the chili, turning it from time to time until it is blistered and black-brown in spots.

Cover the tomatoes with boiling water and simmer until soft -- about 15 minutes, depending on size and compactness. Drain, skin and set aside to cool. For a more robust, earthy flavor, tomatoes can be broiled. Preheat the broiler to medium. Choose a shallow, flameproof dish into which the tomatoes will fit comfortably and can be turned easily (if the pan is too large, then the sweet juice that they exude in the cooking will dry up) and line it with foil. Place the tomatoes on the foil and broil about 2 inches from the flame. As they blister and brown on one side -- try not to char them too much -- turn them over, repeating this process from time to time during the cooking period until they are evenly browned and soft inside -- about 20 minutes for a medium tomato. If any part of the skin has become blackened and rather hard, then peel it off; otherwise blend the whole tomatoes -- skin, seeds, core and all.

Using an electric coffee/spice grinder, grind the toasted seeds, together with the salt, to a coarse powder. Transfer to a small serving bowl. Stir the tomatoes into the ground pumpkin seeds, together with the coriander, chives and whole chili (if you prefer a more picante dish, blend the chili with the tomatoes before mixing them with the seeds). Serve at room temperature.

The mixture should have the consistency of mayonnaise. If it is too thick, you may have to add a little water to dilute it. OSTIONES PIMENTADOS (Pepper Oysters) (6 to 8 servings) 4 dozen oysters, removed from shells and liquid reserved 2 teaspoons whole peppercorns 1/2 teaspoon salt, or to taste 6 cloves garlic 1 tablespoon lime juice, more if desired 2 tablespoons olive oil 1 bay leaf

Heat the liquid from the oysters to the simmering point, then add the oysters and poach for 2 to 3 minutes, or until the edges start to curl up. Drain the oysters, reserving the broth.

Pound the peppercorns in a mortar with the salt until finely ground. Pound in the garlic and gradually add the lime juice. Last of all, add about 3 tablespoons of the reserved oyster broth. Mix well. l

Heat the olive oil in a saucepan. Add the bay leaf and the peppercorn mixture and cook over a high flame for about 3 minutes, stirring constantly. Remove the pan from the flame and add the oysters. Adjust the seasoning, then add a squeeze of lime juice and a little of the oyster liquid if desired.

Set aside to cool and serve as suggested above, or leave to season overnight. BARBACOA DE CARNERO OAXAQUENO Oaxaca Barbecued Mutton) (6 to 8 servings) For the barbecue sauce: 3 chiles anchos 8 chiles guajillos 2 tablespoons sesame seeds 1 1/4 inch piece cinnamon bark 2 tablespoons vinegar 2/3 cup water, approximately 3 large cloves garlic, toasted and peeled 1/4 teaspoon thyme 1 teaspoon oregano 1 1/2 teaspoons salt, or to taste For the meat: 3 to 4 pounds mutton* or lamb (mutton is preferable but inexpensive cuts of lamb such as lamb shanks can be used; poundage will depend on how much of the mutton or lamb is bone) 2 large sprays avocado leaves (optional) 2 teaspoons salt For the dough; 2 ounces (1/4 cup) pork lard, softened 2 teaspoons salt, or to taste 2 pounds tamal dough or 4 cups masa harina plus 2 1/2 cups water

To prepare the sauce, slit the chiles anchos open and remove the seeds and veins; remove the stalks from the chiles guajillos, but leave the seeds and veins. Toast the chilies well on a hot griddle. To toast, flatten them out as much as possible on the griddle, turning them from time to time so they do not burn; if they do, the sauce will have an acrid flavor. As the inside becomes opaque and the outside begins to blister slightly, remove the chilies and let them cool off. There should be a strong, earthy aroma to them, and if they have toasted sufficiently, when cool they should be brittle and crumble easily. If the chilies are very fresh and pliable, it may take 8 to 10 minutes for them to reach this point. Cover the chilies with water and bring them to a boil. Remove from the flame and let them soak for 5 minutes.

Meanwhile, put the sesame seeds into an ungreased frying pan over a low flame. Keep turning them over until they turn a rich golden color, then set them aside to cool. When they are cool, put them, together with the cinnamon, into a spice grinder and grind as fine as possible (this step may seem unnecessary, but if you put all the ingredients into the blender together the sesame seeds would remain whole for the most part).

Drain the chilies and put into a blender jar. Add the vinegar, water, garlic, herbs, salt, and ground sesame mixture and blend until almost smooth -- the sauce should have a little texture, and it should be quite thick, rather like a paste.

To prepare the meat, salt it, then cover it liberally with the chili sauce, leaving about 2 tablespoons aside to add to the dough later. Set the meat aside to season.

Preheat the oven to 400 degrees.Have ready a roasting pan into which the meat and avocado leaves (if using), will just fit comfortably. Put a rack ino the pan and add 1 cup of cold water. Pass both sprays of avocado leaves over the bare flame or a very hot electric burner -- they should sizzle, crinkle, and send off a rich avocado smell. Place one of the sprays on the rack in the pan. Set the pan and the other avocad-leaf spray aside while you prepare the dough.

Work the lard, salt, and reserved chili sauce into the tamal dough. (if you are using masa harina , add these ingredients along with the water and mix to a soft dough.) Divide the dough into 2 equal parts. Pat each part out into a roughly circular shape about 3/4 inch thick. Place the meat on one piece of dough and top with the second piece; press the edges of the dough together so that the meat is completely covered.

Place the dough-covered meat on the avocado leaves in the pan and cover with the second spray. Cover the pan with a well-fitting lid or foil tightly secured to the edges of the pan so that practically no steam will escape.

Place the pan on the middle rack of the oven and bake for 1 hour. Turn the oven down to 325 degrees and cook until the meat is tender -- about 3 hours, depending on the quality and cut of the meat. During the cooking time maker sure that there is still some liquid in the bottom of the pan -- you may have to add 1/2 cup or so more of water to keep the dough moist (at the end of the cooking time the meat should be very soft; there should be some sauce around it and the dough should be spongy and moist). t

Cut the meat and serve with plenty of the dought, along with freshly made tortillas, frijoles refritos (well-fried or refried beans) and strips of chiles jalapenos en escabeche (pickled chilies).

*Note: Available at the Americana Grocery, 1813 Columbia Rd. NW. PUERCO EN NARANJA (Pork Cooked in Orage Juice) (6 to 8 servings) 5 pounds rib-end pork loin (in 2 pieces, if necessary, to make up this weight) 5 cloves garlic, peeled 1 tablespoon salt 2 teaspoons oregano 12 peppercorns 3 oranges

Pierce the meat all over with the point of a sharp knife. Crush the garlic together with the salt, oregano and peppercorns, and moisten with the juice of 1 orange. Rub this mixture into the pork and set aside to season for 1 hour.

Preheat the oven to 350 degrees.

Place the pork in a heavy casserole into which it will just fit comfortably and moisten it with the juice of a second orange. Add the skin of the orange to the casserole, then cover and bake for 2 hours.

Drain off all but about 3 tablespoons of the pan juices and reserve. Turn the meat over and bake for another hour, uncovered, basting the meat from time to time.

Drain off the pan juices again and reserve. Turn the oven up to 400 degrees and brown the top of the meat, then turn it over and brown the other side.

Meanwhile, skim the reserved pan juices of most of their fat. Add the juice of the third orange and reduce quickly over a high flame. Slice the meat and either pass the sauce separately or spoon it over the sliced meat at the moment of serving. TORTILLAS (16 5-inch tortillas) 2 cups masa harina or 1/2 to 3/4 pound prepared masa* 1 1/3 cups water (for masa harina) Tortilla press, preferably the 6-inch size 2 small polyethylene bags (alligator-textured)

If you are using prepared masa , you will not, of course need the water. If using masa harina , put it in a mixing bowl, add the water all at once (this will keep lumps from forming) and mix together quickly, just until the ingredients are combined. Set the dough aside for 20 minutes. While the dough is resting, place you heavy griddle or griddles (using 2 will speed up the process) over a medium flame and let heat up throughly; you should be able to hear the dough sizzle faintly when a tortilla is placed in it if the griddle has been heated to the proper temperature.

After the resting period, make you first tortilla, to test the consistency of the dough. (if you are using prepared masa , start following the directions at this point.)

Open the tortilla press and place one of the polyethylene bags on the lower part. Roll a piece of the tortilla dough into a ball 1 1/2 inches in diameter and place on the bag, slightly more toward the hinge than the handle of the peress. Put the second polyethylene bag carefully on top. Close the press and push the handle firmly down, then open it up and carefully peel off the bag on top. Remove the second bag, with the tortilla on it, and invert it, so the dough side is down, on your other, upturned hand, on the fingers rather than the palm as much as possible. Very carefully peel the bag from the dough (not the other way around) and lay the tortilla on the hot griddle. Do this slowly and evenly; if you just drop the tortilla on the griddle, you will get air bubbles and the dough will not cook properly.

Look at the tortilla on the griddle. If it looks thick, with a grainy, uneven edge, the dough is too dry. Work a little -- only a little more water into the dough in the bowl; you don't want to make the dough sodden and unmanageable. (If you had trouble peeling the bag off the tortilla in your hand, it may be too damp; sprinkle a very small amount of masa into the bowl, mix it in briefly and try again.)

If your tortilla seems right, or when your dough reaches the right consistency, cook the tortilla on the hot griddle until it just begins to dry out around the edges. At that point, flip it over and cook it on the second side for a slightly longer time, until it just begins to color. Flip it back onto the first side and finish cooking it through (the whole process, if the heat is right, should take about 2 minutes). You will be able to tell if you dough is really the right consistency and cookin at the proper temperature if the tortilla puffs up when you flip it back onto the first side. Remove it from the griddle and wrap it in a thick towl or napkin.

Proceed with the rest of the dough, checking it from time to time to see if it is drying out and adding a little water if it is. As each tortilla is finished, stack it with the previous ones, and keep well wrapped in the towel, so they staty warm and flexible.

*Note: Available at Casa Lebrato, 1729 Columbia Rd. NW. All recipes from Diana Kennedy's "Recipes from the Regional Cooks of Mexico."