Heat a large saucepan and fry the onion in a splash of oil until soft and translucent.
Add the carrots, garlic and ginger and heat through for a couple of minutes, then stir in the curry powder.
Add the peanut butter, stock, coconut milk, brown sugar, lime leaves and chilli - and heat the soup through for about 5 minutes.
Add the lime juice, fish sauce, green pepper and chicken, and heat the soup through for a couple of minutes.Meanwhile, cook the noodles according to the packet instructions.
Season the soup with salt and pepper - and more fish sauce, lime and chilli if needed.
Divide the noodles between 4 bowls, pour over the soup and sprinkle with spring onions and chopped peanuts.