01 - Combine the beef with 2 tbsp soy sauce, cornstarch, and sesame oil in a medium bowl. Toss to coat evenly and let marinate for 10 minutes at room temperature.
02 - Whisk together 3 tbsp soy sauce, oyster sauce, hoisin sauce, chili garlic sauce, rice vinegar, brown sugar, and water in a small bowl until sugar dissolves. Set aside.
03 - Heat 1 tbsp vegetable oil in a large skillet or wok over high heat. Add beef in a single layer and sear for 1-2 minutes per side until browned but not fully cooked. Remove and set aside.
04 - Add remaining 1 tbsp oil to the pan. Stir fry garlic and ginger for 30 seconds until fragrant, being careful not to burn.
05 - Add broccoli and bell pepper to the pan. Stir fry for 2-3 minutes until vegetables reach tender-crisp consistency.
06 - Return beef to the pan with green onions. Pour in sauce and stir well. Cook for 2-3 minutes until beef is cooked through and sauce thickens slightly.
07 - Remove from heat. Sprinkle with toasted sesame seeds and fresh cilantro. Serve immediately over steamed rice or noodles.