Slice beef thinly against the grain. Toss with baking soda, cornstarch, soy sauce, cooking wine, and white pepper. Marinate for 15 minutes.

Mix the sauce: combine oyster sauce, dark soy sauce, sesame oil, sugar, and 2 tablespoons water in a small bowl. Set aside.

Heat 1 tablespoon oil in a wok over high heat until smoking. Add beef in a single layer and sear for about 1 minute until just cooked. Remove to a bowl.

Add remaining oil to the wok. Stir-fry onion and carrot for 1 minute, then add bell pepper and bok choy. Cook for another minute until crisp-tender.

Return beef to the wok. Pour in the sauce and toss everything together for 30 seconds until the sauce is syrupy and coats the ingredients.

Garnish with green onions and serve immediately over steamed rice.