Mix together the fish sauce, lime juice and sugar with 4tbsp water in a small bowl. Toss the chicken slices in chilli powder. Heat 2tbsp of oil in a large frying pan or wok and fry the chicken until cooked through with no pink showing. Drain to a plate. Add the greens and fry until beginning to wilt and drain to the plate. Heat the remaining oil and fry the mushrooms, spring onions and garlic until golden. Return the chicken and greens to the pan along with the noodles, breaking them up with a wooden spoon. When the ingredients are heated through, pour in the fish sauce mixture and mix well. Pile onto plates and serve scattered with peanuts and coriander. Shiitake mushrooms were originally harvested in the Far East and are still associated with Asian cooking. Their firm texture works brilliantly in stir-fries and here we've made a popular Thai noodle dish called pad Thai.
