In a bowl, combine the sliced chicken with 1 tablespoon soy sauce and 1 tablespoon cornstarch. Toss until evenly coated and let marinate for 15 minutes while preparing the other ingredients.
In a separate bowl, whisk together soy sauce, oyster sauce, hoisin sauce, sesame oil, cornstarch, chicken broth, sugar, grated ginger, and minced garlic. Mix until smooth and set aside.
Prepare the chow mein noodles according to package directions. Drain and set aside.
Heat vegetable oil in a large skillet or wok over medium-high heat. Add the marinated chicken and stir-fry for 4–5 minutes, stirring constantly, until fully cooked. Remove from the skillet and set aside.
In the same skillet, add the onion and carrots. Stir-fry for 2–3 minutes until slightly tender. Add cabbage and bean sprouts and cook another 2 minutes, keeping the vegetables crisp-tender.
Return the cooked chicken to the skillet. Add the drained noodles and pour the prepared sauce over the top. Toss everything together and cook for 2–3 minutes until evenly coated and heated through.
Stir in sliced green onions, give it one final toss, and serve hot. Garnish with extra green onions if desired.