Depending on your preference, you can make this Cantonese dish with asparagus or bell peppers. Serve with hot rice and garnish with cilantro sprigs, if you like.
In a bowl, stir together cornstarch, soy sauce, 1 teaspoon of the water, and sherry. Add chicken and stir to coat; then stir in 1 1/2 teaspoons of the oil and let marinate for 15 minutes.
Meanwhile, prepare Cooking Sauce and set aside. Seed bell peppers and cut into 1-inch squares. (Or snap off and discard touch ends of asparages; cut spears; cut spears into 1/2-inch slices.)
Place a wok over high heat; when wok is hot, add 1 tablespoons of the oil. When oil begins to heat, add black beans and garlic; stir once. Add chicken mixture and stir-fry until meat is no longer pink in center; cut to test (about 3 minutes). Remove from wok and set aside.
Pour remaining 1 tablespoon oil into wok; when oil is hot, add bell peppers and onion and stir-fry for 1 minute. Add remaining 1 tablespoon water and cook, uncovered, until vegetables are tender-crisp to bite--2 to 4 more minutes. (If using asparagus, add 2 tablespoons water; cook, covered, for 3 to 4 minutes.)
Stir together 1 tablespoon each soy sauce and cornstarch, 1/4 teaspoon sugar, and 1/3 cup regular-strength chicken broth or water.