Soak the chillies in boiling water for 10 minutes to soften. Once soft make a paste with them using pestle and mortar or a hand blender.
Bring plenty of water to the boil in a medium saucepan and turn off the heat. Blanch the noodles for 8 minutes without the lid, drain and run cold water over them, drain again and set aside.
Heat a wok or large frying pan over a high heat and add the 2 tablespoons of oil. Saute the garlic for 5 seconds or so, then add the prawns. Cook until the prawns start to turn pink. Add the chilli paste and fry for 30 seconds, then add the noodles, the two soy sauces and the spring onions. Fry for 2 minutes, until the noodles have soaked up the sauce.
Push the noodles to one side of the wok and drizzle in a little more oil. Break in the egg and let it scramble, then stir into the noodles. Add the beansprouts and cook for 1 minute then serve.