01 - Combine beef with soy sauce, cornstarch, and sesame oil in a bowl. Mix thoroughly and let marinate for 10 minutes.
02 - Whisk together soy sauce, oyster sauce, hoisin sauce, rice vinegar, sriracha, sugar, and water in a small bowl. Set aside.
03 - Heat vegetable oil in a wok or large skillet over high heat. Add marinated beef in a single layer and sear for 1-2 minutes until browned. Remove and set aside.
04 - Add garlic and ginger to the wok, stir-frying for 30 seconds until fragrant.
05 - Add bell peppers, carrot, and snow peas. Stir-fry for 2-3 minutes until tender-crisp.
06 - Return beef to the wok, pour in the prepared sauce, and toss everything for 1-2 minutes until heated through and slightly thickened.
07 - Stir in sliced spring onions, then remove from heat.
08 - Sprinkle with toasted sesame seeds and chopped cilantro or extra spring onions. Serve hot with steamed rice or noodles.