Cook the noodles according to the instructions on the packet. Drain and set aside.
Heat a large frying pan and add 2 tablespoons of the vegetable oil. When really hot, add the noodles, flattening them down so that they cover the bottom of the pan. Cook over a high heat for 3–4 minutes until golden brown and crispy. Once they have coloured on the first side, turn the noodles over and brown on the other side as well. Stir in the sesame seeds.
Meanwhile, heat the remaining oil in a wok, add the ginger and garlic and stir-fry for 1 minute, then add the prawns and stir-fry for 2 minutes until turning pink. Add the soy sauce and sweet chilli sauce and bring to the boil, then reduce the heat and simmer for 1–2 minutes until the prawns are pink and firm. Finally, add the pak choi and stir until the leaves begin to wilt.
Place the noodles on a large plate and top with the prawns and pak choi. Sprinkle with the spring onions and coriander and drizzle with the sesame oil.