This quick stir-fry features broccoli and flank steak in a flavorful sauce. This dish is typical of many traditional Chinese stir-fries--the sauce just clings to the beef and vegetables but is not enough to spoon over rice. Marinating beef is essential for ensuring the meat is flavorful. The meat does not marinate overnight, as in traditional Western recipes. The moment the beef is combined with the seasonings it is ready to be stir-fried.