Cook the noodles in a pan of boiling water until al dente. Scoop out some of the noodle water and drain.
Meanwhile, heat the oil in a small non-stick frying pan over a medium heat. Crack in the egg and cook for 2-3 minutes until the white sets and edges go a little crispy.
Melt the butter in the noodle pan whilst they drain. Add the gochujang, soy sauce, noodles, spring onions and 2 tbsp of the noodle water. Mix together until glossy. Transfer to a bowl and top egg and serve immediately with chilli oil and sesame seeds if you like.
