01 - Combine sliced chicken with soy sauce, cornstarch, and sesame oil in a bowl. Let marinate for at least 10 minutes to tenderize and infuse flavor.
02 - Whisk together soy sauce, oyster sauce, hoisin sauce, sugar, white pepper, and water in a small bowl until smooth and fully incorporated. Set aside for later use.
03 - Prepare noodles according to package directions until al dente. Drain thoroughly and rinse under cold water to stop cooking. Toss with 1 teaspoon oil to prevent sticking.
04 - Heat 1 tablespoon oil in a large wok or skillet over high heat until shimmering. Add marinated chicken and stir-fry until just cooked through, about 3 to 4 minutes. Remove from wok and set aside.
05 - Add remaining 1 tablespoon oil to the wok. Sauté garlic and onion for 1 minute until fragrant. Add carrot, bell pepper, and snow peas; stir-fry for 2 to 3 minutes until vegetables are crisp-tender.
06 - Return chicken to the wok. Add cooked noodles, bean sprouts, and spring onions. Pour in prepared sauce and toss everything together over high heat for 2 to 3 minutes until well combined and heated through. Serve immediately.