Dinner in December -- oh dear! Poultry is preempted by the holidays; your favorite fish can be scarce because of winter storms; the quality of vegetables is uncertain and hardly any fruits are genuinely in season. When discouraged, I turn to my favorite experts and at once my negative attitude to winter is put to shame.

French revolutionary gastronome Grimod de la Reynie re composed seasonal menus for December and was able to recommend 25 dishes in a dinner for 15 and topped that with 46 dishes for 40 people. Escoffier revels in oysters, baby lamb, quail, partridge, chestnuts, endive, truffles, and, of course, foie gras. Nearer our own day, Simca Beck feasts on shellfish, game, stews, and chocolate desserts. The oysters, lamb, chestnuts, celery root, cranberries, walnuts, and tropical fruits I've assembled for this menu really only touch on the many seasonal possibilities.

The oysters as appetizer are served hot, baked in their shells on a bed of duxelle -- mushroom pure'e -- and coated with a watercress and cream sauce. The recipe recalls oysters rockefeller with a lighter, fresher approach. If you're far from the coast and a supply of fresh shucked oysters, try the same recipe with sea or bay scallops, spreading them on the mushroom pure'e in ramekins or shallow individual baking dishes, then coating them with sauce and broiling like the oysters. If watercress for the sauce is not available, spinach may be substituted.

Leg of Lamb 'en chevreuil' is so very French. The lamb is marinated for two or three days, giving it a dense aromatic flavor reminiscent of game -- at half the price. Unscrupulous restaurateurs have been known to serve "venison" that is nothing more than marinated lamb and "wild boar" that started out as pork. (For the truth, look at the bones; wild animals are more frail than domestic ones.)

Call the lamb mock venison from the beginning and you'll be surprised how much it resembles the real thing. The marinade imbues the lamb with the same flavors used to perfume and tenderize game. The acid in a marinade breaks down the fibers and these same acids help to preserve it -- a godsend in the not-so-long past prerefrigeration era. Of course, if you know a generous hunter or are blessed with a venturesome grocer, use the real thing. And don't limit yourself to roast game. Those unctuous French game ragouts are based on the same marinade.

All the classic accompaniments are appropriate -- rich brown sauce with red-currant jelly and more than a hint of black pepper; pure'es of seasonal vegetables such as celery root, turnip, pumpkin, rutabagas and chestnuts. Here I've combined celery root and chestnuts, a happy marriage I discovered in a neighborhood Paris bistro last winter. Pure'es are little work nowadays, thanks to the food processor, but unfortunately they cannot be reheated because their starch content turns to glue. However, keeping them hot an hour or two in a water bath will do no harm.

To add color to the plate I suggest a confit of cranberries. Confit means a preserve that is cooked very long and slowly so it is meltingly soft and, in the case of fruits, transparent when cooked. Onions make a great confit, as do leeks and radishes, and here the cranberries are baked with butter and sugar so they soften very gradually while keeping their shape.

After two substantial courses, dessert must not overwhelm, so I've suggested a salad of tropical fruits to accompany delicate bavarian creams flavored with walnuts. The fruit salad contains a minimum of fruit -- star fruit or pineapple, orange, and kiwi -- but it is a great opportunity to add others -- persimmon, passion fruit, papaya, or what you will. Rum adds zest and, given the cream's richness, you probably won't need sugar.

Key to a good bavarian cream is the use of gelatin; there should be just enough to hold the egg custard and cream without becoming rubbery. Gelatin stiffens on standing in the refrigerator, so be sure to leave the cream an hour or two at room temperature if it is prepared ahead. When grinding the walnuts, avoid too fine a powder and leave a few pieces of nut to provide texture to the whipped eggs and cream. If you are fond of cinnamon, you may increase the amount in the recipe -- this odd combination is surprisingly good.

In fact the whole menu is a challenge -- a grouping of unusual flavors and methods of cooking. It's a dinner to intrigue any connoisseur. TIMETABLE

One to three days ahead: Marinate lamb in refrigerator. Make cranberry confit and refrigerate.

Up to one day ahead: Make bavarian cream and refrigerate.

Up to four hours ahead: Prepare ingredients for hot oysters and keep in refrigerator. Make fruit salad and chill.

Two hours before serving: Drain meat and pat dry. Boil marinade until reduced by half. Heat oven to 400 degrees. Make chestnut and celery root pure'e and keep warm in a water bath. Turn out and decorate bavarian cream. Set the table and chill white wine.

One and one-half to one and three-quarters hours before serving: Brown lamb and start roasting in oven; baste it often during cooking.

Fifteen minutes before serving: Take out lamb and turn oven to broil; keep meat warm and make the sauce.

Five minutes before serving: Assemble and broil oysters, turn oven to low and warm cranberries.

After serving oysters: Arrange lamb on a platter and decorate with chicory. Transfer chestnut and celery pure'e and cranberry confit to serving dishes. Pour sauce into a sauceboat.

This is a leisurely timetable, the kind I like. Plenty can be done ahead, so that the predinner workload is light, leaving space for a relaxed glass of wine with guests. Dessert is completed well ahead, taking pressure off the cook once the main course is served. HUITRES CHAUDES A LA DUXELLE ET AU CRESSON (Hot Oysters with Mushroom Duxelle and Watercress) (8 servings)

Try this recipe also with cherrystone clams. 3 bunches watercress, stems discarded Salt and Pepper 1 1/2 cups cre me fraiche or heavy cream Pinch of nutmeg 48 oysters, shucked, bottom shells reserved For the duxelle: 1 tablespoon butter 1/2 onion, finely chopped 3/4 pound mushrooms, finely chopped Rock salt (for baking)

Bring a large pan of salted water to a boil, add watercress and bring just back to a boil. Drain, rinse under cold water and drain thoroughly. Squeeze watercress dry. Pure'e it with the cream in a blender or food processor. Boil watercress mixture in a heavy saucepan until it thickens slightly, about 3 minutes, and season to taste with salt, pepper and nutmeg. Let cool to room temperature .

For duxelle: In a frying pan melt butter and saute' onion until soft but not brown. Add mushrooms, salt and pepper and cook, stirring occasionally until all moisture has evaporated and mixture is quite dry, about 5 minutes.

Spread rock salt on a large heatproof platter or 8 individual baking dishes. Wash and dry oyster shells and put a teaspoonful of duxelle in each. Top duxelle with an oyster. Oysters can be prepared up to 4 hours ahead and refrigerated. To serve: light the broiler. Spoon watercress sauce over oysters. Set oysters 4-5 inches from heat and broil until hot, 3-5 minutes. Serve at once. GIGOT D'AGNEAU EN CHEVREUIL, SAUCE GRAND VENEUR (Mock Venison, Pepper and Red-currant Sauce) (8 servings)

So the lamb is easy to carve, be sure the butcher removes any backbone and the hipbone, leaving only the thigh and leg bones. FOR THE MARINADE: 3 cups dry red wine 2 onions, sliced 3 carrots, sliced 4 shallots, sliced Bouquet garni of 1 sprig thyme, 1 bay leaf, and 6 parsley stems 2 tablespoons red wine vinegar 2 cloves garlic, peeled 2 tablespoons oil Pinch of sugar Pinch of salt 2 teaspoons peppercorns FOR THE LAMB: 5-6 pound leg of lamb 1 tablespoon butter 2 tablespoons oil Salt and pepper 1 teaspoon arrowroot mixed to a paste with 1 tablespoon cold water 2-3 teaspoons red-currant jelly 1/4 cup heavy cream 2 tablespoons cold butter, cut in small pieces (to finish sauce) Head of chicory, divided into leaves (for garnish)

For marinade: Combine all marinade ingredients in a saucepan and simmer 10 minutes. Leave to cool completely. Put meat in a deep bowl and pour marinade over; meat should be completely covered with marinade. Cover and refrigerate 1-3 days, depending on taste you prefer. Turn meat from time to time.

Drain meat and pat dry with paper towels; strain marinade, reserving liquid and vegetables. Heat butter and oil in a roasting pan and brown lamb on all sides. Spread reserved vegetables in roasting pan underneath the meat. Roast in a 400-degree oven, allowing 12 minutes per pound for pink meat, or 15 minutes per pound for well-done meat. Note: A shorter time than usual is needed for roasting as the meat has been "cooked" slightly in the marinade. Baste meat from time to time during cooking. Meanwhile, boil marinade until reduced by half.

Test cooking by inserting a skewer in thickest part of meat: If warm to the touch when withdrawn after half a minute, meat is pink. For well-done lamb, continue cooking 10 minutes longer. When done, remove meat from roasting pan, cover loosely with foil, and keep warm.

For sauce: Discard excess roasting fat from pan. Add marinade and cook on top of stove, stirring to dissolve pan juices. Strain into a saucepan and bring to a boil. Whisk in arrowroot paste, stirring constantly until sauce has thickened slightly. Add red-currant jelly and stir until melted. Add cream, bring just back to a boil and take from heat. Season with a generous quantity of freshly ground black pepper: the sauce should be quite piquant. Note: Do not boil sauce once pepper has been added or sauce will be bitter. Take sauce from heat and whisk in remaining butter, in small pieces, until melted. Set lamb on a platter and garnish it with chicory leaves. Serve sauce separately. PUREE DE MARRONS ET CELERI (Chestnut and Celery Root Puree) (8 servings)

Turnips or rutabagas are alternatives if celery root is hard to find. 2 pounds chestnuts Salt and pepper 3 pounds celery root Juice 1/2 lemon 1 1/2 cups half-and-half, more if necessary 4 tablespoons butter Grated nutmeg Milk

In a saucepan bring chestnuts with cold water to cover to a boil. With a slotted spoon remove a few at a time and peel them with a sharp knife while still hot. Put peeled chestnuts in a pan of salted water, cover and simmer until very tender, 20-25 minutes. Drain and let cool slightly. Work them through a sieve or food mill or pure'e in a food processor.

While chestnuts are cooking, peel celery root, cut in large chunks and put at once in a pan of water with lemon juice. Celery root discolors easily, so work quickly. Cover and simmer until tender, 20-25 minutes. Drain thoroughly. Work through a sieve or food mill, or pure'e in a food processor. Note: If using food processor, pure'e must be worked through sieve to remove fibers.

In a large saucepan combine chestnut and celery pure'es. Add half-and-half, butter, salt, pepper and nutmeg and cook, beating constantly, until pure'e is very hot and slightly thickened. It should just fall easily from the spoon; if too thick, add more half-and-half. Taste for seasoning.

Pure'e can be prepared up to 2 hours ahead and kept warm in a water bath. Pour a layer of milk on top to prevent a skin forming. Just before serving beat milk into pure'e and transfer it to a serving dish. CONFIT D'AIRELLES (Confit of Cranberries) (Makes about 3 cups confit, 8 servings)

If you like cranberries sweet, add half a cup more sugar. 2 tablespoons butter 1 pound cranberries, rinsed and picked over 1 cup sugar

Spread half the butter in a shallow baking dish and add cranberries. Sprinkle them with sugar and dot with remaining butter. Cover dish with foil and bake at 350 degrees until cranberries are tender and all liquid has evaporated so cranberries are very shiny, about 1 hour. If cranberries produce too much juice during cooking, remove foil after 45 minutes so liquid evaporates.

Confit can be made up to 3 days ahead; keep it in the refrigerator. Reheat in low oven until warm and transfer to a serving bowl. BAVAROIS AUX NOIX (Walnut Bavarian Cream) (8 servings) 1 1/2 cups walnut pieces, ground 1 teaspoon ground cinnamon 3 cups milk 1 vanilla bean, split lengthwise or 1/2 teaspoon vanilla extract 2 envelopes gelatin 1/4 cup cold water 9 egg yolks 1/2 cup sugar 3 tablespoons dark rum 1 cup whipping cream, whipped until it holds a soft shape 8 walnut halves (for decoration) Salade de fruits exotiques (recipes follow)

Mix ground walnuts and cinnamon.

For bavarian cream: scald milk with vanilla bean (not extract), cover and leave to infuse 10-15 minutes. Sprinkle gelatin over water in a small pan and leave until spongy, 5 minutes. Beat egg yolks with sugar until thick and light. Whisk in half the hot milk and whisk mixture back into remaining milk. Heat gently, stirring constantly with a wooden spoon until custard thickens slightly; if you draw a finger across the back of the spoon it will leave a clear trail. Note: Do not overcook or it will curdle. At once strain into a metal bowl. If using vanilla extract add it now.

Melt gelatin over very low heat and stir into hot custard. Leave to cool, stirring occasionally. When cool, set custard mixture over a bowl of ice water. Stir until mixture starts to set. Stir in ground walnuts. Fold in rum and whipped cream as lightly as possible. Note: Work fast as the mixture sets quickly once it is cold. Pour mixture into ramekins, cover, and chill at least 2 hours or up to 24 hours.

To finish: If made ahead, let molds stand at room temperature an hour until cream softens slightly. To turn out, run a knife around the edge and pull mixture away from the mold with a finger to release the airlock. Dip bottom of mold in a bowl of warm water a few seconds. Set large dessert plate upside down on top, turn over and give a sharp shake so bavarian falls onto plate. Arrange fruit salad overlapping around each bavarian and put one walnut half on top. SALADE DE FRUITS EXOTIQUES (Tropical Fruit Salad) (8 servings)

Persimmon, passion fruit, papaya -- add exotic fruits as you wish. 3 star fruit or 1 small pineapple 4 seedless oranges 3 kiwis 2-3 tablespoons rum

Slice star fruit into 1/4-inch slices or peel pineapple, cut into 1/2-inch slices, remove core and cut each slice in half.

With a sharp knife, peel oranges, removing skin and pith. Segment the oranges, discarding all membrane. Peel the kiwis and slice in 1/4-inch slices.

In a glass or stainless steel bowl, gently mix the fruits with the rum. Cover tightly and chill. Fruit salad can be prepared up to 4 hours ahead and kept in the refrigerator. Serve chilled.