Heat the chicken stock in a pan over a medium heat. Add the lemon grass, galangal and lime leaves. Bring to the boil and throw in the prawns, mushrooms and coconut. Simmer gently until the prawns turn pink and are tender.
Meanwhile, mix together the lime juice, fish sauce and chilli paste. Stir this mixture into the soup when the prawns are cooked. Heat through for a minute or two, then serve sprinkled with the chillies and coriander leaves.
© 1994 Keith Floyd estate. All rights reserved.