1. Prepare the chicken:

Slice the chicken thinly for even cooking. In a bowl, combine the sliced chicken with soy sauce, cornstarch, and sesame oil. Mix well and set aside to marinate for at least 10 minutes while you prepare the other ingredients.

2. Make the sauce:

In a small bowl, whisk together soy sauce, oyster sauce, hoisin sauce, sugar, sesame oil, chicken broth, and cornstarch. Set the sauce aside.

3. Cook the noodles:

Bring a large pot of water to a boil. Add the chow mein noodles and cook according to the package instructions (typically 2-3 minutes). Drain the noodles and rinse them under cold water to stop the cooking process. Drizzle a little sesame oil over the noodles and toss to prevent sticking.

4. Sauté the chicken:

Heat 1 tablespoon of vegetable oil in a large wok or skillet over medium-high heat. Add the marinated chicken and cook for 4-5 minutes, stirring frequently, until fully cooked and slightly golden. Remove the chicken from the wok and set aside.

5. Stir-fry the vegetables:

In the same wok, add the remaining tablespoon of vegetable oil. Sauté the onion and garlic for 1 minute until fragrant. Add the cabbage, carrots, and bell peppers, stirring for another 2-3 minutes until the vegetables are crisp-tender. If using bean sprouts, add them during the last minute of cooking.

6. Combine and cook:

Return the cooked chicken to the wok, then add the noodles. Pour the prepared sauce over the mixture and toss everything together to coat evenly. Stir-fry for 2-3 minutes, allowing the sauce to thicken and coat the noodles.

7. Garnish and serve:

Remove the chow mein from heat and garnish with chopped green onions. Serve hot, either on its own or with additional side dishes.