Marinate the chicken while you prepare the rest of the ingredients
1 pound chicken breast (about 2 breasts), cubed
3 scallions, whites only, thinly sliced on an angle
2 cloves garlic, minced
1-inch piece peeled fresh ginger, minced
1 tablespoon soy sauce
2 tablespoons sugar
1 tablespoon, plus 1 teaspoon cornstarch
1 1/4 teaspoons salt
1 tablespoon dry sherry
1 tablespoon dark sesame oil
About 1/3 cup water
3 tablespoons vegetable oil
5 to 6 cups broccoli, trimmed sliced stalks and medium florets (keep the 2 cuts separate)
3/4 to 1 teaspoon red chili flakes, optional
1 tablespoon hoisin sauce
Garnish: toasted sesame seeds, optional
Serving suggestion: Jasmine rice