In a large bowl, combine sliced flank steak with baking soda, Shaoxing wine, light soy sauce, oyster sauce, white pepper, water, and cornstarch. Mix thoroughly and let marinate for at least 15 minutes.

Whisk together oyster sauce, light soy sauce, dark soy sauce, Shaoxing wine, sugar, chicken broth, and cornstarch in a bowl until smooth.

Bring a pot of water to boil, add salt, and blanch broccoli florets for 1-2 minutes. Drain and rinse with cold water.

Heat a wok or large skillet over medium-high heat. Add oil and then the marinated beef in a single layer. Sear for about 30 seconds on each side.

In the same skillet, add garlic and ginger, sauté for about 30 seconds. Then add blanched broccoli and cook for 1 minute.

Return the beef to the pan, pour in the prepared sauce, and toss everything together. Allow to thicken for 1-2 minutes.

Drizzle with toasted sesame oil, check that beef is cooked and broccoli is crisp-tender. Serve hot over steamed rice.