Heat the rapeseed oil in a wok or large frying pan, add the mushrooms and stir-fry over a high heat for 3 minutes until browned and tender.
Mix together the mirin or sherry, soy sauce, sugar, ginger and sesame oil in a jug and add to the pan. Cook, stirring occasionally, for 3–4 minutes until the sauce has reduced slightly and coats the mushrooms.
Meanwhile, cook the rice noodles and sugar snap peas in a saucepan of boiling water for 2 minutes, or until the noodles are tender and the sugar snap peas still have a crunch to them. Drain and return to the pan, then add the sweet chilli sauce and toss to lightly coat.
Divide the noodles and sugar snap peas between 4 bowls and spoon the mushrooms and sauce over the top.