01 - Combine sliced beef with 1 tablespoon soy sauce, 1 teaspoon cornstarch, and 1 teaspoon sesame oil in a bowl. Mix thoroughly and let marinate for 10 minutes.
02 - Whisk together soy sauce, oyster sauce, hoisin sauce, rice vinegar, brown sugar, garlic, ginger, cornstarch, and water in a separate bowl. Set aside.
03 - Heat 1 tablespoon vegetable oil in a large wok or skillet over high heat. Add marinated beef in a single layer and stir-fry for 2 to 3 minutes until browned. Remove from wok and set aside.
04 - Add remaining 1 tablespoon vegetable oil to wok. Stir-fry carrots for 2 minutes, then add snow peas and continue stir-frying for another 2 minutes until vegetables are crisp-tender.
05 - Return beef to wok, pour in prepared sauce, and stir to combine. Cook for 1 to 2 minutes until sauce thickens and coats beef and vegetables evenly.
06 - Remove from heat, garnish with sliced spring onions if desired. Serve immediately over steamed rice or noodles.