TWO MONTHS into the new year and my mail, as usual, has been heavy with questioning letters: "Now that you have spent another year eating your way around, please tell us which you think is the greatest restaurant on earth?" And -- as if that isn't tough enough to answer -- there is often a second related question: "If we were able to dine at the greatest restaurant, which would be the best dish to order from the menu?"

These are, of course, impossible questions. But the questions are so genuinely enthusiastic and transparently honorable that I never can resist trying to find reasonable answers.

These are four truly great cuisines in the world and they are, in order of their brilliance, diversity, depth of pleasure and technical French and the Moroccan. The greatest Chinese and Indian preparations are banquet dishes, which are almost never obtainable in restaurants. There is only one Moroccan restaurant of world stature -- in far-away, hard-to-reach Marrakech. So the world restaurant scene is dominated by the French. Assuming that their home ground -- with the largest supply of great cooks and products -- is Belgium. France and Switzerland, the famous Michelin Guide awards its top three-star rating to 17 names but does not differentiate among them. Obviously, some are greater than others.

The very greatest chefs of the very greatest restaurants consider it their duty to be in front of their stoves at all times when meals are being served. This brings my personal list down to three supreme chefs and their restaurants: Paul Haeberlin and his Auberge de l'Ill in Alsace, Roger Verge and his Moulin de Mougins in Provence, and Fredy Girardet and his restaurant on the shore of Lake Geneva in Switzerland.

Choosing among these three is tougher than the biblical judgement of Solomon. But if I were strapped into the electric chair and ordered to make up my mind or suffer the worst. I would choose for the sheer beauty and peace of the restaurant, for the delicacy and perfection of its food, plus the country simplicity and warmth of the welcome and the service, the supreme Auberge de l'Ill of Alsace, run by Paul Haeberlin and his son, Marc, in the kitchen, with Paul's brother, Jean-Pierre, in the dining room, with the two wives, and a dedicated staff.

Every important restaurant critic has said, at one time or another, that the Auberge de l'Ill is "hours concours," without peer. Jean-Pierre Haeberlin is an artist of rare ability who has designed and decorated what is probably the most beautiful restaurant in France, in a terraced garden on the bank of the tiny, slow-moving, swan populated River Ill as it meanders softly through the Alsatian village of Illheusern.

Whether you are strolling along the village street village outside the front door (the village of which Jean-Pierre Haeberlin is mayor) or sipping your aperitif in the willow-shaded garden, or sitting at table at one of the huge picture windows, the atmosphere is of the depth and repose of the country in beautiful, rural Alsace. It is all a pure vision of delight. It has the warmth of a family welcome into a country home.

But there is nothing simplistic or unsophisticated what Jean-Pierre said to me the first time I dined there, about 20 years ago: "The most significant thing about us, monsieur, is that my brother and I were born in a room above this restaurant. We are not imported into this region. We and our food are products of the Alsatian earth!" Here is not imitation of Parisian haute cuisine. Paul, with his mature wisdom -- to which Marc now adds the audacity of youth -- has rethought it, recast it, improved and glorified it to a marvelous delicacy and lightness, with elegance and refinement. The final result is a dazzling parade of near-magical rejuvenations of the supreme Alsatian country dishes.

Among so many splendors, which is their greatest dish? Who can say? It's a matter of personal taste. But I do know which is their most famous. More than 50 years ago -- when they were a tiny country bistro and the Michelin Guide had never even heard about them -- when automobile touring was only for a few rich people -- the Haeberlin family bistro became renowned locally for a single dish, cooked perfectly by the grandmother of the present brothers. It was a classic "matellotte d'anguille Alsatienne," a kind of local, creamy bouillabaise -- stew of fat eels and other fish caught in the river at the back door of the restaurant.

Paul Haeberlin has served me the equisite fish stew many times. Finally, a few months ago, he gave me a practical workout of the recipe for preparation in a home kitchen. I have adapted it to American ingredients and the techniques of an American kitchen. Our eels are not quite as fat as those of Alsace, but a reasonably small quantity added to a balanced mixture of other fish, supplies a wonderful richness of flavor and solidity of body. Matelotte is not really a soup, you do not have to serve it in a bowl or deep plate -- it is a solid stew of largish chunks of fish covered with a creamy, winey sauce. It is one of the greatest classic dishes of France. This version deserves to be the most famous dish of the greatest restaurant. PAUL HAEBERLIN'S MATELOTTE, A STEW OF FISH IN THE MANNER OF HIS GRANDMOTHER (6 to 8 servings) About 4 1/2 pounds mixed, firm-fleshed fish, must be at least 1 pound of eel, plus, if possible, halibut, monkfish, perch, pike, trout, etc., each in large chunks, skinned; can be boned, but better flavor and more even cooking if bones are left in About 11 tablespoons unsalted butter 1/4 cup peeled and minced shallots 1 bottle fine dry Alsatian riesling white wine About 2 1/2 cups clear fish fumet, preferably made by preboiling fish bones with aromatic vegetables, but can be replaced by bottled clam juice Course crystal or kosher salt and freshly ground black pepper 3 tablespoons chopped fresh leaf of thyme, in season, or 1 tablespoon dried Freshly ground nutmeg, to taste 2 cups all-purpose flour 3/4 pound small buttom mushrooms, stalks pulled off and trimmed 1 whole fresh lemon, for squeezing 4 large egg yolks 1 1/4 cups whipping cream

Kitchen equipment: Large 4-quart lidded stewpot, cutting board with sharp knives, nutmeg grater, large slotted spoon, wooden spatulas and spoons, lemon squeezer, large 3-quart lidded saucepan, saute pan for mushrooms, mixing bowl and balloon wire whisk for egg yolk, aluminum foil.

Average time required: About 30 minutes to prepare and poach the fish, plus about 20 minutes more to make the sauce, assemble the matelotte and serve it. Poaching the Fish

Set the large stewpot on medium frying heat and melt in it 2 tablespoons of the butter.When it is fairly hot, but not in any way browning, sprinkle in the minced shallots and stir them around until they are limp and transparent -- usually in 3 or 4 minutes. Stop the sauteing at once by pouring in and stirring around the first two cups of the wine. Next, mix in the first two cups of the fish fumet. Also stir in the thyme and a couple of grinds of the nutmeg. Let it all simmer gently, to blend the flavors, for no more than 5 minutes.

Begin poaching the fish -- each type timed according to the firmness of its flesh -- in this aromatic bouillon. First, slide in the pieces of eel because they require the longest cooking. Five minutes after the liquid has returned to gentle bubbling, slide in the remaining fish. If necessary, to cover the fish, add more wine and fumet in equal amounts. The total poaching time should be no more than about 20 minutes -- sometimes less.

Watch, the fish, prod with a long fork, and taste little bits here and there. With the experience of a couple of tries, you will know the timing for your stove. If you are using different types of fish, judge the firmness of the flesh (and the bubbling time needed) by pressing it with the tips of your fingers. While the poaching is in progress, warm up a large serving platter.

Meanwhile, in your large saucepan, gently melt 5 more tablespoons of butter and work it into the flour as soon as itis liquid. When they are thoroughly blended, take them off the heat and let them cool. Preparing the Cream Sauce

The moment the fish is perfectly cooked, carefully take out all the pieces with a slotted spoon and keep them warm on the serving platter, covered with aluminum foil. Boil the poaching liquid hard for just about 5 minutes, to concentrate and magnify the flavors. Now blend the hot liquid, gradually, stirring it all the time, into the butter-flour mixture until everything is completely worked together. Put it all back in the stewpot and bubble it (not hard) for about 10 minutes. Meanwhile, in a saute pan, lightly saute the 3/4-pound of mushroom caps and trimmed stalks in the remaining butter. Do not overcook them. Turn off the heat and hold them in the pan.

When the timer rings for the 10 minutes of boiling, taste the sauce and season with salt and pepper. Now give the sauce a light, lemony taste by squeezing in, spritz by spritz, as much fresh lemon juice as you like. Stir in the mushrooms. Just before serving, beat together in a separate bowl the egg yolks and the heavy cream. Then work this carefully and gradually, into the sauce. Reheat it, extremely gently, stirring all the time and making sure that it does not reach anywhere near to the boiling point. At the last moment, pour the sauce over the fish and serve at once, on very hot plates. In Alsace, the accompaniment would be homemade egg noodles.