In a medium bowl, combine the flank steak with baking soda, Shaoxing vinegar, light soy sauce, oyster sauce, and white pepper. Allow to marinate for at least 15 minutes.

While the beef is marinating, mix 2 tablespoons of water with 1 tablespoon of cornstarch in a small bowl to create a slurry.

In another bowl, whisk together the remaining marinade ingredients and add chicken broth. Set aside.

Heat a wok or large skillet over high heat, add vegetable oil, and sear the marinated beef in batches for 1-2 minutes on each side.

In the same wok, add broccoli and stir-fry for 2-3 minutes until tender-crisp.

Add minced garlic and grated ginger, stirring until fragrant for about 30 seconds.

Return the seared beef to the wok, add the savory sauce, and let it simmer for about 1 minute. Gradually add the cornstarch slurry, stirring continuously until thickened.

Serve immediately over steamed rice or noodles.