In a mixing bowl, combine the thinly sliced flank steak with baking soda, Shaoxing wine, light soy sauce, oyster sauce, white pepper, water, and cornstarch. Mix well and allow to marinate for at least 15 minutes.

Prepare the stir-fry sauce by whisking together oyster sauce, light soy sauce, dark soy sauce, Shaoxing wine, granulated sugar, chicken broth, and cornstarch in a small bowl.

Bring a medium pot of salted water to a boil, add broccoli, and blanch for 1-2 minutes. Drain and set aside.

Heat 1 tablespoon of oil in a wok over medium-high heat. Add the marinated beef in a single layer, searing for about 30 seconds on each side. Remove and set aside.

In the same wok, add another tablespoon of oil. Sauté minced garlic and ginger for about 30 seconds. Add blanched broccoli and stir-fry for 1 minute. Return beef and pour in stir-fry sauce, tossing together for 1-2 minutes.

Turn off the heat, drizzle toasted sesame oil over the stir-fry, and serve immediately.