Marinate the Beef: Combine the flank steak with baking soda, Shaoxing wine, light soy sauce, oyster sauce, white pepper, water, and cornstarch in a large bowl. Let it marinate for at least 15 minutes.

Prepare Stir-Fry Sauce: In a separate bowl, whisk together 1.5 tbsp oyster sauce, 1 tbsp dark soy sauce, sugar, chicken broth, and 0.5 tbsp cornstarch.

Boil Broccoli: Boil salted water, add broccoli and blanch for 1-2 minutes. Drain and rinse under cold water.

Cook Beef: Heat 2 tbsp vegetable oil in a wok over medium-high heat. Sear the marinated beef for 30 seconds on each side and remove from the pan.

Stir-Fry: Add another tbsp of oil, sauté minced garlic and ginger for 30 seconds, add broccoli, then the beef and stir-fry sauce. Cook until sauce thickens, about 1-2 minutes.

Serve: Drizzle with toasted sesame oil and serve hot, garnished with green onions if desired.