Cook the noodles according to the packet instructions and drain. Toss in a teaspoon of the sesame oil to prevent them sticking together. Toss the salmon with the honey, soy sauce and chilli flakes. Heat a non-stick frying pan or wok over a high heat. Add the sesame seeds, toast until they are lightly golden, and then remove from the pan. Add a teaspoon of sesame oil to the pan and once hot, cook the salmon for about a minute each side or until golden (reserving any of the honey and soy left behind in the dish). Remove from the pan and keep warm.
Add the remaining teaspoon of the sesame oil to the pan and quickly fry the noodles, spring onion and bean sprouts until the noodles are heated through. Add the spinach, sesame seeds and any remaining honey and soy mixture from the salmon. Toss until the spinach is starting to wilt. Tip the noodles and spinach mixture into a serving bowl. Sit the honey-seared salmon on top and serve straight away.