01 - Toss beef strips with cornstarch, 1 tbsp soy sauce, and sesame oil. Let marinate for 10 minutes.
02 - Whisk together soy sauce, oyster sauce, chili garlic sauce, rice vinegar, brown sugar, and water in a small bowl.
03 - Heat 1 tbsp vegetable oil in a large wok or skillet over high heat. Add beef and stir-fry for 2–3 minutes until browned but not fully cooked. Remove and set aside.
04 - Add remaining 1 tbsp oil to the pan. Stir-fry garlic, ginger, and onion for 1 minute until fragrant.
05 - Add bell peppers, carrot, snap peas, and broccoli. Stir-fry for 3–4 minutes until crisp-tender.
06 - Return beef to the wok. Pour in sauce and toss to coat all ingredients. Cook for 2–3 minutes until beef is cooked through and sauce has thickened.
07 - Serve hot with steamed rice or noodles if desired. Garnish with sesame seeds or sliced green onions.