In a bowl, mix together the flank steak, baking soda, Shaoxing wine, light soy sauce, oyster sauce, white pepper, water, and cornstarch. Let marinate for at least 15 minutes.

In a small bowl, combine the oyster sauce, light soy sauce, dark soy sauce, Shaoxing wine, granulated sugar, chicken broth, and cornstarch. Set aside.

Bring a pot of salted water to a boil. Add the broccoli and cook for 1-2 minutes until bright green and tender-crisp. Drain and set aside.

Heat oil in a large pan over medium-high heat. Sear the marinated beef in a single layer for about 30 seconds on each side until browned. Remove from pan.

In the same pan, add more oil and sauté minced garlic and ginger for 30 seconds until fragrant. Add the blanched broccoli and cook for 1 minute, stirring gently.

Return the beef to the pan and pour in the prepared sauce. Stir-fry for 1-2 minutes until the sauce thickens and clings to the beef and broccoli.

Turn off the heat and drizzle the toasted sesame oil over the dish. Toss gently to combine.