01 - Combine sliced flank steak with 1 tablespoon soy sauce, 1 teaspoon cornstarch, and 1 teaspoon sesame oil in a medium bowl. Toss to coat and let rest for 10 minutes.
02 - In a small bowl, whisk together oyster sauce, 2 tablespoons soy sauce, Shaoxing wine, sugar, 2 teaspoons cornstarch, and 1/3 cup plus 1 tablespoon water until smooth. Set 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 beef and set aside.
04 - Add the remaining 1 tablespoon vegetable oil to the wok. Stir fry the minced garlic and grated ginger for 30 seconds until fragrant.
05 - Add broccoli florets and 2 tablespoons water to the wok. Stir fry for 2 to 3 minutes until broccoli turns bright green and is just tender.
06 - Return the beef to the wok. Pour in the prepared stir fry sauce and toss to combine. Cook for 2 to 3 minutes until the sauce thickens and coats the beef and broccoli thoroughly.
07 - Serve immediately, optionally accompanied by steamed rice.