Marinate the Beef: In a small bowl, combine water, cornstarch, vegetable oil, oyster sauce, and baking soda (if using). Add the sliced beef, tossing to coat evenly, and set aside to marinate for 10-15 minutes.

Prepare the Stir-Fry Sauce: In another bowl, mix hot water, sugar, hoisin sauce, dark soy sauce, light soy sauce, sesame oil, and white pepper. Stir until well combined.

Cook the Tofu: Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Add the tofu cubes and cook until golden on all sides, about 5 minutes. Remove and set aside.

Stir-Fry the Beef: Add another tablespoon of oil to the skillet. Sear the marinated beef for 1-2 minutes, until just browned. Remove and set aside.

Sauté Aromatics: Add the remaining ½ tablespoon of oil to the skillet, then add ginger slices, garlic, and the white parts of the scallions. Sauté until fragrant, about 1 minute.

Combine Ingredients: Add bell pepper and tofu to the skillet, followed by the Shaoxing wine. Return the beef to the pan, pour in the stir-fry sauce, and stir well to coat everything evenly.

Finish and Serve: Cook for another 1-2 minutes, tossing in the green scallion parts at the end. Serve hot over steamed rice.