1. In a wok, heat 2 tablespoons of the oil. Add the chicken sausage and stir-fry over high heat, breaking it up, until just cooked through, 3 minutes. Transfer to a plate.
2. Heat the remaining 3 tablespoons of oil in the wok. Add the garlic and ginger and stir-fry over moderately high heat until golden, 1 1/2 minutes. Off the heat, stir in the snow peas and chilies for 1 minute. Add the orange juice and stir over moderately high heat for 30 seconds. Add the sausage, noodles and stock mixture (stock mixed with hoisin sauce and cornstarch), season with salt and stir-fry until the sauce is thickened, about 2 minutes. Remove from the heat, stir in the basil and serve.