Marinate the beef: In a bowl, combine the thinly sliced beef with cornstarch, baking soda, soy sauce, dark soy sauce, oyster sauce, Shaoxing wine, sugar, salt, white pepper, and minced garlic. Mix well and let the beef marinate for 15 minutes to absorb all the flavors.
Prepare the sauce: In a small bowl or large measuring cup, whisk together the water, soy sauce, oyster sauce, dark soy sauce, sugar, cornstarch, white pepper, and salt until fully blended. Set aside.
Cook the beef: Heat oil in a large wok over high heat. Once the oil is hot, add the marinated beef in an even layer. Sear the beef for 2-3 minutes per side until nicely browned, making sure not to overcook it.
Add the sauce: Pour the prepared sauce over the seared beef. Stir and cook until the sauce thickens, about 1-2 minutes, thanks to the cornstarch in the marinade.
Blanch the broccoli: While the beef cooks, blanch the broccoli florets in boiling water for about 30 seconds. Drain well and add the broccoli to the beef. Stir gently to coat the broccoli with the sauce.
Serve: Spoon the beef and broccoli over a bed of steamed white rice, or enjoy it on its own for a flavorful, protein-packed dish.