Cook the egg noodles as described on the packet, then immediately drain and refresh in ice-cold water.
Cut the bell pepper into 2-3cm (1-1¼") long batons.
Top and tail the green beans and cut into 2-3cm (1-1¼") lengths.
Cut the chilli in half lengthways, remove the seeds and then cut into strips as thin as you can and around 2-3 cm (1-1¼") long.
Top and tail the red onion, peel it, then cut it into 8 wedges.
Mix together the sweet chilli sauce, Chinkiang vinegar and soy sauce with the cornflour and set aside.
Cut the salmon into 3cm (1¼") cubes.
Heat a wok over a high heat, and when it is shimmering hot, add the oil.Then, in with the salmon and gently stir-fry for 2-3 minutes before removing and setting aside.
Add the red onion and chilli pepper, then stir-fry for 1 minute.
Throw in the green beans and bell pepper and stir-fry for 2 minutes.
Then add the drained noodles and bean sprouts and cook for a minute.
Return the salmon to the pan and pour over the sauce, and toss to coat, and then cook for a final minute or 2 to reheat the salmon.