EVERY YEAR around this time, root parsley makes its annual appearance on the market for a few weeks or so, and I take out a family recipe for that great Belgian dish, waterzoi.

Most recipes for this delicate but aromatic poached chicken in a lemony, creamy sauce call for parsley sprigs as a prime flavoring. The best of them, which comes from my husband's Belgian Aunt Suzanne, uses root parsley, also called parsley root or Hamburg parsley. This ingredient looks like a small parsnip and tastes like a combination of celeriac (celery root) and parsley. It gives the Waterzooie a wonderful underbody and freshness.

The chicken pieces are cooked with julienned root parsley, leeks, carrots and celery along with chicken stock, then presented on a large platter along with the vegetables and some minced parsley for more color. The dish is then served in flat soup plates with plenty of sauce ladled over it from a separate tureen. The Waterzooie is eaten with a fork, knife, soup spoon and good french bread.

The first course provides a contrast in color, texture and flavor to the chicken. Little bamboo skewers of hot, broiled chicken livers are teamed with fans of Belgian endive leaves. A madeira sauce for the livers also serves as a warm dressing for the salad. The combination is mildly startling but successful and very pretty.

The meal ends with the nice clean taste of buttery baked apples in white wine made tart with red currant jelly.

The little bamboo skewers for the chicken livers should soak in a pan of cold water for a good six hours so that they will be thoroughly saturated to prevent them from being burned to a cinder under the broiler. The livers can marinate anywhere from two to six hours. I prepare the brochettes just before our guests arrive. Five liver halves are threaded on each skewer with a single strip of bacon, which snakes between and around the livers in a continuing "s" shape. The skewers are then placed in a roasting pan large enough not to crowd them but small enough to fit under the broiler. This pan, which can easily be removed from the oven every time the skewers need turning, avoids the problem of food sticking to the broiler. It also saves the cook from having to kneel on the floor or, in my case, stand on tiptoe to get to the broiler, and it catches the juices as well. Once the livers are cooked, a sauce can be made by deglazing the pan with the leftover marinade. Individual plates are then prepared with one brochette and three fanned endive leaves.

I prefer blade (unground) mace for the Waterzooie because it is more subtle than ground nutmeg. Blade mace can be found among better spices at supermarkets and at the Bethesda Avenue Coop. Root parsley is sold in bunches at Giant stores, where it will be available for another couple of weeks, and at Hudson Brothers, where it will be in stock for somewhat longer. I discard the leaves of root parsley, which look like flat Italian parsley but lack its flavor, as well as the stalks. Root parsley, which must be peeled, is also an excellent addition to a chicken stock pot or vegetable soups or stews. Celeriac can be combined with parsley in the Waterzooie if root parsley is unavailable.

The only real preparation required for the Waterzooie involves cutting the carrots, leeks, root parsley and celery stalks into a matchstick julienne. The most efficient tool for this is not a machine but rather a good chef's knife. Those who are more casual about how food looks can use the processor to produce a passable julienne with root vegetables, although not with leeks and celery. Alternatively, all the vegetables could be chopped coarsely in a processor. However, the hand-cut matchstick julienne gives the dish a finished, festive look.

The sauce for the Waterzooie is bound at the last minute with egg yolks, lemon juice and cream. It is important that the sauce not be allowed to boil once the enrichment is added. At this stage, it should be stirred constantly and the pot should be removed from the heat the minute a simmer bubble appears. Should the sauce boil, it might curdle, in which case it will not be smooth and beautiful, but the flavor will still be good.

I did the baked apples with mcintoshes, staymans and jonathans. For flavor, the mcintoshes were far superior. However, since mcintoshes do not hold their shape as well as the others when baked, you should watch carefully the last minutes of baking and should not let them overcook. The apples can be baked a day in advance, if necessary, and heated in a moderate oven for about twenty minutes before serving. CHICKEN LIVERS EN BROCHETTE WITH ENDIVE (8 servings) 8 bamboo skewers 1 1/2 to 1 3/4 pounds chicken livers (about 20 whole chicken livers) 1/2 cup medium-sweet madeira wine 1/4 cup olive oil 1 teaspoon dried tarragon 1/4 teaspoon coarsely ground black pepper 8 red radishes 24 leaves (about 3 long heads) Belgian endive 8 strips bacon, uncooked

About 6 hours before the livers are to be cooked, set the bamboo skewers to soak in a pan of cold water.

From 2 to 6 hours before the livers are to be cooked, split them, remove all membranes, fat and greenish spots, drain and put into a bowl. Add the madeira, olive oil, tarragon and pepper, cover and refrigerate.

Wash the radishes and cut off the stem and the root ends. With a small knife (a curved-bladed fluting knife is easiest), make parallel vertical slices through the radish but do not cut through the bottom. Start slicing at the middle and work down to each end. Drop them into a bowl of ice water and refrigerate until needed.

Wash the endives, cut off the root ends and carefully detach 24 large outside leaves. Dry and refrigerate in a plastic bag until needed.

Remove the livers from the marinade but reserve the marinade. Thread the skewers (this can be done at least an hour in advance) by starting with the end of a slice of bacon, then half a liver, then through the slice of bacon, and continue until the skewer holds five pieces of liver. The bacon ribbons around the liver, forming a continuous "s".

Swirl the skewers in the marinade, place them in a roasting pan large enough not to crowd them and refrigerate until they are to be cooked. Place the pan under a preheated broiler, about 3 inches from the flame, for 7 to 8 minutes. Remove the pan and turn the skewers every 3 minutes or so, to cook the livers evenly. Make a tiny gash in one liver at the end of the cooking time to test for doneness. The livers should be pink but not bloody. Place a skewer on each serving plate. Add the remaining marinade to the roasting pan and bring to a boil, scraping the brown bits into the sauce with a wooden spoon. Then arrange three leaves of endive on each place in a fan shape, and place a drained radish flower at the base of the fan. Finally, spoon the juices over the livers. Serve immediately. WATERZOOIE OF CHICKEN (8 servings) 2 2- 1/2 to 3-pound frying chickens, each cut into 8 pieces Salt and freshly ground white pepper to taste 1/2 cup butter 4 large ribs celery, cut into a 2-inch-long matchstick julienne 3 large carrots, trimmed, peeled and cut into a 2-inch-long matchstick julienne 4 leeks, white part and an inch of green, trimmed, split and washed under cold running water, then cut into a 2-inch-long matchstick julienne 2 bunches root parsley (about 10 small roots), trimmed, peeled and cut into a 2-inch-long matchstick julienne, or 15 sprigs fresh parsley, tied into a bundle with string, and 15 small knobs of celery root (celeriac), peeled and cut into a 2-inch-long matchstick julienne 3 blades mace or 1/4 teaspoon nutmeg 6 cups chicken broth Juice of 1 lemon, or more, to taste 4 eggs yolks 3/4 cup heavy cream 4 tablespoons chopped parsley

Salt the chicken pieces lightly and pepper them moderately heavily. Melt the butter in a heavy, large ovenproof casserole and add the chicken. Cover and stew the chicken without browning it for about 10 minutes, turning the chicken occasionally. The skin will have started to firm and take on a yellow color. Add the julienned vegetables, the parsley bouquet if you haven't found root parsley, and the mace or nutmeg. Then add the chicken broth and bring to a simmer. Cover and cook over low heat for about 30 minutes, or until the chicken is tender. The chicken can sit in this broth while you are having your first course.

Just before serving, heat the broth to boiling and remove the chicken to a heated flat serving platter. Discard the parsley bouquet if you have used one. With a slotted spoon remove the julienned vegetables and strew these over the chicken pieces. Add the lemon juice to the broth and heat to a simmer. Beat the yolks lightly with the cream and gradually add this to the hot broth. Cook over low heat for a couple of minutes to slightly thicken the sauce. Stir constantly and do not let it boil. Ladle some of the sauce over the chicken and sprinkle with the minced parsley. Then pour the remaining sauce into a heated tureen.

To serve, place some chicken in a low, flat soup plate and ladle some sauce over it. Accompany with warm, crusty french bread. BAKED APPLES WITH CURRANT JELLY IN WHITE WINE (8 servings) 8 large mcintosh apples 8 tablespoons red currant jelly 4 teaspoons unsalted butter 1 1/2 cups dry white jug wine 6 tablespoons sugar

Core the apples, using either an apple corer or a melon baller. Arrange them in a baking dish and place a tablespoon of the red currant jelly in each. If the cavity isn't large enough, let the jelly spill over. Then place 1/2 teaspoon butter on each apple. Mix the wine with the sugar and pour around the apples. Bake in a 375-degree oven for 40 minutes, or until the apples are tender but not overcooked. The more these apples are basted during baking, the better they will be. Serve hot, lukewarm or at room temperature, never cold.