Put the noodles into a bowl and cover with freshly boiled water. Heat two tsp oil in a wok or large non-stick frying pan over a high heat. Stir-fry the mushrooms for two minutes or until golden.
Add the remaining oil and the tofu pieces, and cook for one minute until hot, then add the cabbage, and cook for 2-3 minutes until wilted.
Drain the noodles and add to the pan. Toss with the chilli, soy and mirin. Sprinkle with the salad onions and serve straight away.