01 - Combine sliced chicken with soy sauce, cornstarch, and sesame oil in a bowl. Let sit for at least 10 minutes to tenderize.
02 - Whisk together soy sauce, oyster sauce, hoisin sauce, sugar, white pepper, and water in a small bowl until smooth and well combined.
03 - Prepare noodles according to package directions. Drain, rinse thoroughly under cold water, and toss with 1 teaspoon oil to prevent sticking.
04 - Heat 1 tablespoon oil in a large wok or skillet over high heat. Add marinated chicken and stir-fry until just cooked through, approximately 3–4 minutes. Remove from wok and set aside.
05 - Add remaining 1 tablespoon oil to the wok. Sauté garlic and onion for 1 minute. Add carrot, bell pepper, and snow peas; stir-fry for 2–3 minutes until just tender-crisp.
06 - Return chicken to the wok. Add cooked noodles, bean sprouts, and spring onions. Pour in prepared sauce and toss everything over high heat for 2–3 minutes until well combined and heated through.
07 - Transfer to serving plates immediately. Garnish with additional spring onions if desired.