Boil the noodles in salted water for 3 mins until soft. Drain and rinse in cold water. To make the sauce, mix all the ingredients together in a small bowl.
Heat a wok with half the oil. Add the prawns and spring onions, and cook, stirring quickly, for 1 min or until the prawns turn pink. Push to the side and add the remaining oil. Add the egg and let sit for 30 secs, then scramble until cooked. Add the noodles and sauce, and cook, stirring continuously, for 3 mins or until everything is hot.
Serve the noodles with the peanuts and coriander sprinkled on top, and lime wedges for squeezing over.