01 - In a medium bowl, combine the sliced flank steak with 1 tablespoon soy sauce, 1 teaspoon cornstarch, and 1 teaspoon sesame oil. Toss well to coat evenly and allow to marinate for 10 minutes.
02 - Whisk together oyster sauce, 2 tablespoons soy sauce, Shaoxing wine, sugar, 2 teaspoons cornstarch, and 1/3 cup plus 1 tablespoon water in a small bowl. Set the sauce aside.
03 - Heat 1 tablespoon vegetable oil in a large wok or skillet over medium-high heat. Add the marinated beef in a single layer and stir fry for 1 to 2 minutes until just browned. Remove the beef and set aside.
04 - Add the remaining 1 tablespoon vegetable oil to the wok. Sauté minced garlic and grated ginger for 30 seconds or until aromatic.
05 - Add broccoli florets and 2 tablespoons water to the wok. Stir fry for 2 to 3 minutes until the broccoli is bright green and tender-crisp.
06 - Return the beef to the wok. Pour in the prepared stir fry sauce and toss to combine thoroughly. Cook for an additional 2 to 3 minutes until the sauce thickens and evenly coats the beef and broccoli.
07 - Transfer immediately to serving dishes and accompany with steamed rice if desired.