Place the noodles in a saucepan of boiling water and cook for 3 minutes or until tender. Drain. Heat a wok or deep frying pan over high heat. Add the oil, onion, chilli and sugar and cook for 2 minutes. Remove from the pan and set aside. Add the chicken and cook, stirring, for 4 minutes or until the chicken is golden. Add the capsicum, cashews, fish sauce, soy, lemon juice, onion mixture and noodles to the pan. Cook, stirring, for a further 4 minutes or until heated through. Sprinkle with coriander. Serve with chilli sauce. Serves 4.