Add a third of the coconut milk to a saucepan and cook, stirring, over medium heat until the coconut milk starts separating. Stir in the red curry paste and fry for a minute. Stir in the turmeric and fry for a further minute.
Add the remainder of the soup ingredients (except the prawns, lime juice and noodles), cover with a lid and cook over medium heat for ten minutes. Then add the prawns and cook until just done (if they’re small, 2 minutes is plenty). Add the lime juice right at the end.
Dish up warm noodles in a soup bowl and top with coconut broth and prawns. For me curry is all about the toppings, so serve this with spring onions, fresh chilli, coriander leaves, fried garlic and lime wedges on the side and let everyone go mad.