STUFFED CELERY may bring to mind a lackluster cocktail party tray of pimiento cheese dabbed onto a stalk of raw celery, but not if you're from Prato, Italy.

In that prosperous, bustling town on the outskirts of Florence it is pronounced sedani ripieni and appears as crisply fried celery stalks filled with a creamy meat mixture and crowned with tomato sauce and parmesan cheese.

Prato's stuffed celery is not typical of Tuscan cooking, which glories in the simple. Rather, it is a complicated tour de force requiring celery to be thrice cooked: parboiled, deep fried and, finally, baked. The meat filling and tomato-based sauce also call for time-consuming preparation. For this reason, the dish is seldom found in Italian restaurants, even those in Prato. The survival of sedani ripieni depends instead on the home cook -- whether in Prato or Washington -- who is willing to spend a little extra time to create an unusual and succulent dish.

Sedani ripieni is a dish for the first crisp days of autumn, when the palate welcomes slightly heavier, more robust fare and the cook has more patience for kitchen labors. It is also a time when fresh plum tomatoes are still available for the sauce and celery reaches its plump, pale-green peak.

Skinny, bleached stalks will not do. One must seek out bunches with broad, meaty stalks, sometimes sold separately as "large celery." Even then, it is advisable to buy two bunches, cut them in half horizontally and use only the upper halves (away from the bulb) for stuffing.

Sedani ripieni works well as one of several antipasti in a long, luxurious meal. For a lighter meal, however, it is perhaps preferable to serve the stuffed celery as the main course, bounded before and after by less substantial dishes.

The first course could be a soup of homemade broth with fresh pasta. Or move northwest from Prato to Pavia and borrow a few bowls of that town's characteristic soup. Zuppa pavese is nothing but broth, an egg, a slice of bread and a little parmesan, but when each ingredient is of the highest quality, it is a wonderfully light and satisfying soup.

One could follow the stuffed celery with a green salad, and then perhaps a sherbet or fresh fruit. But the meal can end in only one way -- by lingering after coffee over biscotti di Prato, the almond cookies popular in Tuscany and nowadays eaten almost everywhere in Italy. These are invariably dipped, just before each bite, in a glass of vin santo, a sweet dessert wine of ancient lineage. It is mentioned in the letters of Marco Datini, a 14th century Pratese merchant who loved good food and drink almost as much as making money.

The history of biscotti di Prato may be somewhat less venerable than that of vin santo, but the enthusiasm of their boosters cannot be questioned. Rhapsodizing about these cookies, one guidebook says: "They creak under the teeth like new shoes under the step, carrying to the palate the aroma of grain, the smoothness of sugar, the fullness of the sun." This rather curious description is succeeded by the promise that whoever consumes biscotti di Prato at your table will become a friend "between one cookie and the next." Moreover, "When you think you've eaten enough, take a sip of vin santo and your hunger will resurge, a hunger that must at all costs be satisfied."

In all honesty, biscotti di Prato do not merit this praise. They are pleasant cookies of modest pretentions, served in the afternoon when friends drop by or as the finale to an informal dinner. In Tuscany, they turn up in almost any pasticerria, although not all are of equal quality. Some are rock hard, even after dipping, while others are so soft and mealy they disintegrate in the wine. Other faults can include a too-heavy dose of almond extract.

Not surprisingly, the best biscotti di Prato come from the city itself. Asked where to buy superior specimens, any Pratese will direct you unhesitatingly to Antonio Mattei, a pastry shop founded in 1858, where the city's inhabitants line up four deep along the counter on a Sunday morning to buy one- and two-pound sacks of biscotti for the midday meal. Other specialties of the store are brutti e buoni ("ugly and good"), lumpy cookies with gooey centers of almond paste and mantovana, a flat yellow cake containing pine nuts.

Between visits to Antonio Mattei, it is possible to make a decent biscotto di Prato at home. The recipe given here is a modification of Giuliano Bugialli's version in "The Art of Italian Cooking." If you have trouble finding vin santo to accompany the cookies, ask your wine merchant to order it (Alseca Corp. is one Washington importer). ZUPPA ALLA PAVESE (Egg Soup) (6 servings) 6 slices coarse white bread 3 tablespoons butter 1 1/2 quarts seasoned homemade meat broth 6 eggs 1 cup freshly grated parmesan

Fry the slices of bread in butter until golden and crisp. Place one in each soup bowl. Heat the broth to the boiling point. Break an egg over each slice of bread and pour broth slowly from the side into each bowl, taking care not to break the yolk. Pass the parmesan at the table. SEDANI RIPIENI ALLA PRATESE (Stuffed Celery) (4 to 6 servings) For the meat filling:* 3 or 4 pieces of porcini mushrooms (available dried in some Italian groceries), optional 1 onion, chopped 1 tablespoon butter or olive oil 1/4 pound lean ground beef 1/4 pound chicken livers, chopped to a paste 1/4 pound cooked ham, chopped fine 1/4 pound prosciutto, chopped fine 1/2 cup white wine 1 tablespoon flour 2 tablespoons freshly grated parmesan Salt, pepper and nutmeg 1/2 cup milk For the tomato sauce: 32- or 35-ounce can imported Italian tomatoes or 1 1/2 pounds fresh plum tomatoes 1 tablespoon olive oil Basil Salt For assembly: 1 large bunch celery Vegetable oil 1 cup flour 1 or 2 eggs 1 cup fine bread crumbs 1/2 cup parmesan

To prepare the filling, soak porcini mushrooms in 1/2 cup of water for at least 15 minutes. In a skillet, saute' the onion in butter or olive oil until transparent. Add ground meat and stir briefly just until it loses the red color. Do the same with the livers, then stir in the ham and prosciutto. Remove the mushrooms from the soaking liquid, wash carefully to remove all grit and chop coarsely.

Pour the mushroom liquid through a sieve lined with a paper towel into another bowl. Add the mushrooms to the other ingredients in the pan. When the mixture is well blended and fairly homogeneous, pour in the wine and the mushroom liquid and allow to simmer until almost evaporated. Sprinkle the flour over the mixture and stir continuously for two to three minutes. Add the cheese, salt and pepper to taste, a little nutmeg and the milk. Simmer 15 minutes longer.

Make a simple sauce by putting the canned tomatoes in a saucepan with olive oil and a few leaves of basil. Cook the mixture down for about 15 minutes until dense. Or cut fresh plum tomatoes in half, cook in the same way and force through the fine sieve of a food mill. Season with salt and set aside. The sedani ripieni can be made a day or two ahead of time up to this point.

Peel each celery stalk and cut into two or three sections, depending on length (allow four to six sections for each person). Boil the celery in plenty of salted water for about 10 to 15 minutes, until tender but still firm. Let the stalks cool slightly; then flatten each one, splitting it a bit in the middle if necessary. Spread the filling on the concave side of half of the stalks. Place an unfilled celery piece over each filled one and press the edges together (the seal needn't be airtight, for the batter will help hold the bundles together as they fry). Set aside.

Fill a frying pan with vegetable oil to a depth of 1 1/2 to 2 inches. When it is hot (test by dropping in a small crust of bread), dip each celery bundle into flour, egg and bread crumbs. Cook on both sides until brown, then drain on paper towels.

Spread a little of the tomato sauce on the bottom of a casserole large enough to hold the celery in one layer. Line up the celery bundles, sprinkle 1/4 cup parmesan over them, cover with the remaining tomato sauce and top with the rest of the parmesan. Bake at 350 degrees for about 15 minutes or until heated through.

*These proportions will produce more filling than you really need, but using smaller amounts is likely to make it cook too quickly so that it does not reach the proper smooth consistency. In any case, the filling is so useful to have around it seems a shame not to make the full amount. My favorite solution for the leftovers is to make crostini, a popular Tuscan antipasto. Cut a French baguette into thin slices, spread with a little of the meat mixture and heat in a 300-degree oven for about 15 minutes. The filling also can be used inside any stuffed pasta, or thinned with extra tomato sauce or water, as a pasta topping. BISCOTTI DE PRATO (Almond Cookies) (Makes 12 dozen) 8 ounces whole unblanched almonds 4 cups flour 2 cups sugar Pinch salt Large pinch saffron 1 teaspoon baking soda 4 eggs 2 tablespoons Amaretto liqueur or 1/2 teaspoon almond extract (optional) 1 egg white, slightly beaten

Place almonds in 350-degree oven for about 10 minutes or until lightly toasted. Grind 2 ounces very fine, then cut each remaining almond into two or three pieces.

Place the flour in a mound on a cutting board or counter and make a well in the center. Put the sugar, salt, saffron and baking soda in the well and mix. Add the eggs and almond extract or Amaretto, if used. Mix together all ingredients in the well (the broad end of a wooden chopstick works well for this purpose) and then incorporate the flour, little by little.

After kneading the dough briefly, add the ground almonds and almond pieces. Knead for two or three minutes, adding a little more flour if necessary. Divide the dough into 8 pieces and shape each one into a long, thin roll about 3/4 inch in diameter. Space out on two buttered and floured cookie sheets and brush the tops with egg white.

Bake at 350 degrees for about 20 minutes, remove and cool slightly. Slice each roll at a 45-degree angle every 3/4 inch. Lower the oven to 275 degrees, scatter the cookies on the sheets and return to the oven for about 35 minutes. Cool cookies, then place in a paper bag. They will be very dry but will soften a little and taste much better after two or three days. To store indefinitely, transfer to a tin.