Heat the oil in a large frying pan over a medium heat. Add sliced onion and stir for 2 minutes or until soft. Add the sliced mushrooms, increasing the heat slightly and stir-fry for 5 to 10 minutes.
Mix in the crushed garlic stirring for a further minute to blend the flavour into the mushrooms. Add more garlic if desired. Throw in the sliced green and red pepper and season with salt, pepper, cayenne and chilli flakes. Stir-fry for a further 5 to 10 minutes.
Add the heated cooked egg noodles to the frying pan. Mix well and serve.