Heat a large non stick wok over a medium high flame, then add the oil followed by the onion and leeks. Fry for 2 minutes then add the garlic and chilli and cook for a minute.
Add the mushrooms and courgettes, fry for 2 minutes then add the ginger, lemon grass, pak choi and spring greens. Fry for 2 minutes then add the shitake broth, fish and soy sauces.
Bring to the boil, add the noodles and cook for 2 minutes. Remove the wok from the heat and set aside for 1-2 minutes until the noodles are tender. Return to a high heat and serve as soon as the broth bubbles again.