Pour the vegetable stock and coconut milk into a large saucepan and put to simmer on a medium heat.

Add the finely sliced galangal, bruised lemongrass (bash it with the flat side of a knife), 3 of the sliced red chillies, the kaffir lime leaves, prawns, fish sauce and lime juice.

Bring to a simmer and heat for about 6-7 minutes, until the prawns have cooked through.

Add the noodles and chopped herbs, and simmer for a further minute.