01 - Combine sliced beef with 1 tbsp soy sauce, cornstarch, and sesame oil. Toss well and let marinate for 10 minutes.
02 - Whisk together soy sauce, oyster sauce, rice vinegar, chili garlic sauce, brown sugar, and water in a bowl. Set aside.
03 - Heat 1 tbsp vegetable oil in a large wok or skillet over high heat. Stir-fry the marinated beef for 2 to 3 minutes until browned but not fully cooked. Remove and set aside.
04 - Add the remaining 1 tbsp vegetable oil to the wok. Stir-fry onion, garlic, and ginger for 1 minute until fragrant.
05 - Add bell pepper and broccoli florets to the wok. Stir-fry for 2 to 3 minutes until the vegetables become vibrant and just tender.
06 - Return the beef to the wok. Pour in the spicy sauce and toss to coat evenly. Stir-fry for an additional 2 to 3 minutes until beef is cooked through and sauce slightly thickens.
07 - Plate the stir fry hot, garnished with sliced spring onions. Serve alongside steamed rice if desired.