Soak the noodles in a large bowl of warm water for 15 minutes. When soft, drain well. Using scissors or a knife, cut the noodles into 7.5cm/3in lengths.
Heat a wok or large frying pan and add the oil, salt, beansprouts and spring onions and stir fry for 10 seconds. Add the chilli bean sauce, Chinese white rice vinegar, soy sauce, sesame oil and noodles and cook