Chestnuts are about 50 percent water, 45 percent carbohydrate and only 5 percent oil--proportions that are very un-nutlike and the reason chestnuts are the only nut served as a vegetable. In fact, according to Miklos Faust of the Beltsville Agricultural Research Center, chestnuts are closer in content to bananas than to other nuts. And, unlike almonds, English walnuts, filberts and pecans--which average only 3-5 percent water and 25-30 percent oil--chestnut trees grow in the Washington area.

If you are fortunate enough to have a mature chestnut tree--or have access to one--the nuts may be gathered until well after the first frost. That's fun, but then the serious work begins. Some safekeeping steps are in order because chestnuts dehydrate easily and most local chestnuts have tiny worm holes, in which case the weevil larva still may be inside or through which a fungus can enter and destroy the sweet flavor.

It's best to cook chestnuts before storing them. Karen Cozza, a technician at the Northern Virginia Food Preservation Hot Line (691-3428), suggests simmering them at 120 degrees--25 minutes for small nuts, 35 for medium and 45 for large. After that, they can be dried and stored in the shell, or peeled and refrigerated or frozen for later use.

One rotten nut can ruin the batch, according to Faust, chief of the fruit laboratory at Beltsville, who prefers to peel, then cook. He uses a serrated knife to cut off the flat side and peel off the hard shell, discarding any nuts that are dried up or off color. He waits until after boiling to remove the fuzzy, bitter inner skin.

Peeling raw chestnuts is a slow, boring task. Instead, try a technique that can be used safely on the uncontaminated, blemish-free, glossy-brown, imported Italian chestnuts stocked by supermarkets. It's not even necessary to cut a cross in the raw shell. Cover the chestnuts with cold water, slowly bring them to a boil and simmer five minutes. Use a slotted spoon to remove them, one at a time. Cut off the pointed tip and, with the help of a knife, peel off the shell. Or, cut the nuts in half to simplify peeling. Wear rubber gloves if they are too hot to handle. When the chestnuts are hot, the thick outer shell and the silky inner skin come off easily.

Barely cooked, the chestnuts now are ready to be used in soups, poultry stuffings, stews, pure'es, vegetable casseroles and desserts. Marrons glace's (candied chestnuts) are a Christmas treat in France, saute'ed in butter they garnish a roasted bird in Italy, and they are a symbolic food on the New Year's menu in Japan. Canned whole chestnuts packed in water (but not in syrup) and canned unsweetened chestnut pure'e can be substituted for fresh in most preparations, but the taste will be affected.

Once most of the United States east of the Mississippi was covered with forests of American chestnuts, but most of the trees were wiped out by blight between 1904 and 1940. Now Oriental hybrids are the only trees freely grown in this country, but they are not as large or sweet as the European chestnuts (Castanea sativa) we buy at the . As for horse chestnuts, they are an ornamental tree. Once, chestnuts were a staple food all over the world, eaten raw, boiled, roasted or ground for bread. A taste of the old-fashioned chestnut specialties from around the globe demonstrates why they remain popular: ROASTED CHESTNUTS (4 servings)

Chestnuts roasting on an open fire--this romantic scene becomes disappointing when the nuts burn in one spot while remaining raw in another:

Roasting over an open fire: Place chestnuts in the shell in a chestnut roaster or fireproof pan and roast over hot embers until tender, about 30 minutes. Shake often to prevent burning. Pluck the chestnuts from the fire and peel while hot.

Roasting in an oven: Cut a vertical slit on each side of the chestnuts. Spread out on a baking pan and roast at 350 degrees until tender, about 30 minutes. Peel while hot. SAVORY CHESTNUT PUREE (About 2 cups) 2 cups chicken broth 4 tablespoons dry white wine 1 1/2 pounds chestnuts, peeled 5 celery stalks 1 onion, halved 3 tablespoons butter Salt, pepper and cayenne pepper to taste 1 1/2 cups 1/2-inch bread cubes 1/4 cup butter

Bring broth and wine to a boil. Add chestnuts, celery and onion and simmer until tender, about 25 minutes. Remove chestnuts with a slotted spoon and reserve broth. Mash chestnuts or pure'e in a food processor. Add a little reserved broth, 3 tablespoons butter and seasonings. Saute' bread cubes in 1/4 cup butter until golden. Sprinkle over pure'e. %&ENGLISH CHESTNUTS AND BRUSSELS SPROUTS (6 servings) 1 pound chestnuts 1 pound brussels sprouts 3 tablespoons butter 1/2 teaspoon sugar Salt to taste Fresh lemon juice to taste

Boil chestnuts until tender, about 30 minutes. Peel and cut in quarters. Steam brussels sprouts until tender, about 12 minutes. Drain and keep warm. Melt butter in a large skillet and saute' chestnuts until browned. Add sugar, salt, brussels sprouts and lemon juice. Toss well. CHINESE PORK WITH CHESTNUTS (6 servings)

3 1/2 pounds boneless pork 1 1/2 teaspoons sugar 1/2 cup water 5 1/2 tablespoons soy sauce 1/2 pound chestnuts 5 tablespoons dry sherry 1 head cabbage

Cut pork into 1 1/2-inch pieces. Cover with boiling water and simmer 15 minutes. Drain well. Combine sugar, water and 4 tablespoons soy sauce. Pour over pork and bake at 300 degrees 1 hour, stirring occassionally. Cook chestnuts in boiling water until tender, about 30 minutes. Peel and add to pork with sherry and remaining 1 1/2 tablespoons soy sauce. Bake 1 hour. Shred cabbage and boil in salted water until tender. Drain and arrange in a serving dish. Pour pork mixture over top and serve hot with rice. Adapted from "The Complete Encyclopedia of Chinese Cooking," edited by Kenneth Lo. SWEET CHESTNUT PUREE (About 2 cups) 1 1/2 pounds peeled chestnuts 1 1/2 cups milk 1 teaspoon vanilla 1/2 cup sugar 1/4 cup water 2 tablespoons whipping cream Whipped cream for garnish

Place chestnuts in a saucepan with milk and enough water to cover. Add vanilla. Bring to a boil and simmer until tender, about 30 minutes. Pure'e in a food processor. Combine sugar and water and cook to the soft ball stage, 236 degrees on a candy thermometer. Beat hot syrup in a stream into the chestnut pure'e. Beat in cream. Chill in a glass bowl and garnish with whipped cream just before serving. KOREAN SPICED CHESTNUT BALLS (Makes 24) 1 1/2 pounds chestnuts 1/3 cup sugar 1/2 teaspoon ground ginger 1 teaspoon cinnamon 1/2 cup honey 1/2 cup chopped blanched almonds

Cook chestnuts in boiling water until tender, about 30 minutes. Peel. Pure'e in a food processor. Blend in sugar, ginger and cinnamon. Roll into small balls. Dip balls in honey and coat with nuts. Adapted from "The Complete Book of Oriental Cooking," by Myra Waldo. PEKING DUST (6 servings) 2 pounds chestnuts 1 cup sugar 1/4 teaspoon salt 1/2 teaspoon powdered ginger 1 teaspoon vanilla 1 cup whipping cream

Preserved kumquats, slivered glace'ed orange peel, Chinese sugared plums for garnish

Cook chestnuts in boiling water until tender, about 30 minutes. Peel and pure'e in a food processor. Beat in sugar to taste, salt, ginger and vanilla. Beat cream to stiff peaks and fold into pure'e. Chill in a lightly greased bowl or cone-shaped mold. Just before serving, unmold onto a serving platter and garnish with additional whipped cream, kumquats, glace'ed orange peel and Chinese sugared plums. MARRONS GLACE'S (Candied Chestnuts) (Makes 2 1/2 cups) 1 cup sugar 3 cups water 1 vanilla bean, split 1/2 cup light corn syrup 1 pound chestnuts 4 tablespoons brandy

Combine sugar, water, vanilla bean and corn syrup in a large saucepan. Bring to boil and simmer until sugar is dissolved. Cool in pan. Boil chestnuts until tender, about 30 minutes. Peel, leaving whole. Remove vanilla bean and add chestnuts to syrup. Cover and let stand overnight. Bring syrup to a boil, reduce heat and simmer until syrup is thickened (about 45 minutes). Stir in brandy and pour chestnuts and syrup into jars. Store in refrigerator. Serve over ice cream or use to garnish desserts.