Make the sauce by combining soy sauce, Shaoxing wine, oyster sauce, sugar, cornstarch, sesame oil, and water. Stir until smooth; set aside.
Thinly slice the beef against the grain into ¼-inch pieces. Partially freeze the beef first to make slicing easier.
Add 2 tablespoons of the sauce, baking soda, and cornstarch to the beef. Mix well and marinate for 15 minutes.
Heat a wok over high heat until very hot. Add a thin layer of oil, then sear the beef in a single layer for about 2 minutes. Flip and brown the other side for a minute. Transfer to a plate.
Stir-fry the onion and bell pepper for a minute. Add the scallions, then push everything to one side.
Lower the heat slightly. Add a little more oil, then sauté the ginger and garlic until fragrant. Toss with the vegetables.
Return the beef to the pan, then pour in the sauce (stir it again first). Toss until the sauce thickens slightly. Add ground pepper to taste, then turn off the heat.
Video
Notes
Beef: Flank steak, flat iron, sirloin, skirt steak, flap meat, chuck steak, or boneless short ribs work well.
Baking soda: Helps tenderize the beef. Use only a small amount.
Shaoxing wine: Makes the sauce taste better. Use Chinese cooking wine, dry sherry, or sake instead.
Oyster sauce: Makes the sauce savory, a little sweet, and thicker.
Sesame oil: Use toasted sesame oil.
Oil: Use a neutral oil with a high smoke point.
Cooking Tips
Slice the beef thinly against the grain to keep it tender.
Partially freeze the beef to make slicing easier.
Velvet the beef for about 15 minutes to keep it tender and juicy.