Heat a large frying pan over high heat.
Add the oil, lemongrass, chili and spring onion and cook, stirring for 3 minutes.
Place the noodles, chicken, mint, kaffir lime leaves and lemongrass mixture into a large bowl and toss to combine.
In a small bowl, whisk together the lime juice, sugar and fish sauce and pour over the salad.
Refrigerate until serving and serve sprinkled with nuts.