AFTER A workday with the subtleties and occasional outrages of diplomacy, there is nothing like the vigorous chopping, stirring and mixing of a Chinese stir-fry to soothe the psyche. Besides, it's quick, delicious, satisfying and uses whatever ingredients are at hand.

Preparation and cooking time, starting from scratch, is usually not more than half an hour once the techniques are familiar. And the basic dish can be altered easily to fit the whim of the moment and the contents of the refrigerator.

WHIMSICAL CHINESE STIR-FRY (3 servings) 4 tablespoons cooking oil 1/2 to 1 pound beef (thinly sliced round steak is excellent or substitute chicken or pork) 2 to 3 slices ginger root 1 to 2 cloves garlic, minced 2 to 3 dried oriental peppers (substitute 1 teaspoon cayenne or chopped fresh hot peppers) 2 tablespoons black bean sauce 1 tablespoon soy sauce 1 tablespoon sake (substitute dry sherry) 2 medium carrots, peeled and thinly sliced on diagonal 2 stalks celery, peeled and thinly sliced on diagonal 1 green pepper, seeded and diced 1 medium stalk broccoli, stem diced and steamed for 2 minutes; top broken into florets 1 onion, peeled and diced 1/2 cup or more clear chicken bouillon 1 to 2 teaspoons cornstarch dissolved in 2 tablespoons hot water Chopped scallions or fresh coriander and soy sauce for toppings

Put 2 tablespoons oil in a wok or large, heavy frying pan. Add meat and cook until brown on all sides, stirring constantly. Remove meat and wipe wok out with paper towels. Heat 2 more tablespoons cooking oil until smoking hot. Add ginger, garlic and oriental peppers, black bean sauce, soy sauce, sake and any other seasonings you happen to like, cooking until garlic begins to brown, about 1 minute. Add vegetables to wok, beginning with those that require the longest cooking time. (For this recipe, the order to add the vegetables would be carrots, celery, green pepper, broccoli stems, broccoli florets and onion, but you don't have to stick with these. Other suitable ingredients include turnips, yellow or green squash, Chinese or American cabbage, bok choy, bean sprouts, tofu and bamboo shoots. A tomato, peeled and seeded, is also good.) Stir vegetables constantly in oil and seasonings for about 2 minutes.

Add chicken bouillon, stir, cover and steam for 2 to 3 minutes. Do not overcook -- the vegetables should be firm.

Return meat to wok. Add cornstarch mixture and mix well. If dried peppers were used, remove them.

Place on a platter or serve from the wok. The mixture is particularly good over rice, in which case more bouillon might be used, or less cornstarch to keep it saucy. Chopped scallions or fresh coriander are excellent as a final topping. Pass soy sauce for each diner to add his own.