01 - Whisk together soy sauce, oyster sauce, hoisin sauce, cornstarch, water, sesame oil, sugar, and black pepper in a small bowl until well combined. Set aside.
02 - Heat 1 tablespoon vegetable oil in a large wok or skillet over high heat. Add sliced beef and stir-fry for 2–3 minutes until browned but not fully cooked. Transfer beef to a plate and reserve.
03 - Add remaining 1 tablespoon oil to the wok. Add garlic and ginger, stir-frying for 30 seconds until fragrant.
04 - Add asparagus and red bell pepper to the wok. Stir-fry for 2–3 minutes until vegetables begin to soften.
05 - Add bok choy and continue stir-frying for 2 minutes until vegetables are crisp-tender.
06 - Return beef to the wok. Pour prepared sauce over all ingredients. Stir-fry for 2–3 minutes until beef is cooked through and sauce has thickened to coat everything evenly. Taste and adjust seasoning as needed.
07 - Serve hot over steamed rice or noodles. Garnish with toasted sesame seeds or chopped green onions if desired.