1.In a small bowl combine chicken broth, dark soy sauce, soy sauce, oyster sauce, and sugar. Mix well and set aside.
2.In a wok medium heat, add oil and chicken and cook until tender. Transfer to a plate and set aside.
3.Add garlic and onion and cook for 2 minutes. Add the cooked chicken and season with a little salt and pepper.
4.Stir in carrot, napa cabbage, mushrooms, and green beans and cook for 3-4 minutes until a little tender. Add the bowl of sauce and bring to a boil.
5.Add rice noodles and stir until all the noodles are coated with the sauce. Keep on stirring and cooking until the noodles are tender, 3-4 minutes.
6.Season with salt and pepper if necessary. Sprinkle green onions and stir until combined. Serve immediately with lemon wedges.