3/4 lb. flank steak, thinly sliced across the grain
3 tbsps. Chinese black vinegar or balsamic vinegar
1 tbsp. soy sauce
1 tbsp. Chinese rice wine or dry sherry
2 tsp. sugar
2 tsp. chili garlic sauce
1 tsp. sesame oil
Combine marinade ingredients in a bowl. Add beef and stir to coat. Let stand for 10 minutes.
Combine sauce ingredients in a bowl.
Place broccoli in a large pot with 1 inch of boiling water. Boil until tender and crisp, 2 to 3 minutes; drain.
Place a wok over high heat until hot. Add oil, swirling to coat sides. Add garlic and chilies and cook, stirring, until fragrant, about 10 seconds. Add beef and stir fry until no longer pink, 1 1/2 to 2 minutes.
Add broccoli and sauce to wok; bring to a boil. Add cornstarch mixutre and cook, stirring, until sauce boils and thickens. Serve with rice.