Cook the noodles for 7 minutes in a pan of boiling water until al dente, or as per the package instructions.
Drain, then run them under cold running water, and drain again. Drizzle with a few splashes of sesame oil, and toss through to prevent them from sticking.
Season the chicken with a splash of dark soy sauce, the five-spice powder, and chili sauce, if using. Mix well.
Coat the chicken breasts lightly with the cornstarch.
Heat a wok or sauté pan over a high heat, add the peanut oil, and heat until smoking.
Add the chicken, and stir-fry for 2 to 3 minutes, or until cooked through.
Add the red bell pepper, and stir-fry for 1 minute, then the snow peas and green onion and cook for less than 1 minute.
Add the cooked noodles, and season with the light soy sauce, 1 teaspoon toasted sesame oil, and black pepper, to taste.
Stir well and serve immediately.