'Try these steamed meat dumplings," the waitress at a Chinese dim sum restaurant urged my husband and me recently, as she rolled her cart of tempting appetizers toward us. To make sure we enjoyed them, she made a little sauce for us right on the platter, using chopsticks to stir together soy sauce, red rice vinegar and a touch of chili paste. "Be sure to eat the dumplings with this," she said. How right she was! We followed her suggestion, and found the steamed dumplings delicious with the sauce. On their own, they seemed too rich. Not many of us would count vinegar as our favorite ingredient and yet it plays a major role in many cuisines around the world. We got similar advice at a Filipino eatery, where we were encouraged to dip our pieces of grilled chicken in coconut vinegar. It greatly enhanced our enjoyment of the entree. In both cases, the vinegar's sharpness served to balance rich or fatty foods. In fact, it fulfills the same function in its best-known use - in dressings. Vinaigrette dressing, which lends zip to green salads, is named for vinegar, even though the dressing classically has much more oil than vinegar. The vinegar is the key to the dressing's lively flavor. Without it, the dressing would just be oily. And without vinegar, two beloved French sauces - bearnaise and beurre blanc - would be basically butter. Cooks in regions known for their wine generally cook with wine vinegar too. In France, chefs have developed many tasty sauces that depend on this flavorful vinegar for their character. Poultry with vinegar is a particularly popular match in France. A traditional way to prepare a sauce for the luscious meat of roast duck, such as the celebrated canard a l'orange, calls for adding vinegar to the roasting pan to deglaze, or dissolve the roasting juices (after pouring off the duck fat, of course). Then the vinegar is often cooked with sugar to make a dark caramel, which imparts a tart, bittersweet note to the sauce. Chicken braised with vinegar is another beloved dish, especially in the vicinity of Lyon, where cooks pair the region's top-quality Bresse chickens with vinegar made from nearby Burgundy's wine. I sampled a superb version of the dish at the famed Troisgros restaurant in Roanne, in which the sauce is also flavored with garlic. In La Cuisine Lyonnaise by Felix Benoit and Henry Clos Jouve, there are three versions of the dish created by three different chefs. In each of them, the chicken pieces are sauteed, then simmered with a little vinegar and tomatoes or tomato paste. One calls for flavoring the sauce with chopped shallots, another opts for veal stock and a third calls for cooking the chicken in equal amounts of tarragon vinegar and white wine. When using vinegar, here's the primary rule to remember: Be stingy with it. Vinegar is powerful. Even if you have a great bottle of raspberry vinegar, balsamic vinegar or fine wine vinegar, its tartness can easily overpower a dish. A technique suggested in one French recipe is to pour some vinegar into a tiny bottle with a cork, and cut a slit in the cork so you can sprinkle the vinegar through it in a very fine stream, almost drop by drop. A guide to the strength of vinegar is the degree of its acidity, which is labeled on some bottles. Chinese and Japanese rice vinegar, for example, is much milder than French wine vinegar. No matter what kind of vinegar you have, use it with a light hand, then taste the sauce. You can always add more if the sauce needs it. CHICKEN WITH WINE VINEGAR Chicken in vinegar is not only tasty but is easy to prepare, and is a favorite of home cooks. This recipe, which gains a subtle flavor from garlic cloves cooked in their skins, is inspired by the Troisgros version of the dish, which appears in Cuisiniers a Roanne by Jean and Pierre Troisgros. Their sauce is finished with a few tablespoons of butter. To do a kosher version, you could substitute margarine, but I prefer to drizzle the dish with a little extra virgin olive oil. Use either red or white wine vinegar for the dish. Steamed rice and lightly cooked broccoli florets are good accompaniments. A 1.4-kg. to 1.6-kg chicken, cut in pieces Salt and freshly ground pepper 2 Tbsp. extra virgin olive oil, plus a little more for drizzling 15 garlic cloves, unpeeled 3â„4 cup wine vinegar 1 fresh thyme sprig 1 bay leaf 5 or 6 parsley stems 1 Tbsp. tomato paste 2 large tomatoes, peeled, seeded and chopped; or 1 cup canned tomatoes, drained of liquid and chopped 1 cup chicken broth 2 to 3 tsp. chopped parsley Pat chicken pieces dry. Sprinkle lightly with salt and pepper on all sides. Heat 2 tablespoons oil in large heavy skillet over medium-high heat. Add chicken leg and thigh pieces and brown thoroughly on all sides. Set on a plate, using slotted spoon. Add breast pieces to skillet and brown thoroughly. Transfer to plate. Add wing and back pieces to skillet and brown them. Return leg and thigh pieces to skillet. If chicken pieces do not fit in one layer, arrange breast and wing pieces on top. Add chicken juices from plate. Add garlic cloves, cover and cook over low heat for 5 minutes. Add vinegar, thyme, bay leaf and parsley stems and bring to a boil. Simmer uncovered until about half the vinegar's volume has evaporated. Add the tomato paste and chopped tomatoes and bring to a simmer. Cover and cook for 15 minutes or until chicken breast pieces are tender when pierced with a knife. Transfer breast pieces to a platter using slotted spoon. Cover and keep them warm in a low oven. Add chicken broth to pan. Continue cooking remaining chicken pieces about 10 minutes more or until all are tender. Add leg and thigh pieces to platter. Discard back pieces. Skim as much fat as possible from sauce in skillet. Cook sauce until concentrated and well flavored. Remove thyme sprigs and bay leaf. Strain sauce, pressing firmly on garlic cloves to extract the flavor. Return sauce to pan and reheat. Taste and adjust seasoning, adding a little more vinegar if desired. Spoon sauce over the chicken, drizzle with olive oil and sprinkle with chopped parsley. Serve immediately. Makes 4 servings. The writer is the author of Fresh from France: Dinner Inspirations and of Faye Levy's International Chicken Cookbook.