Bruise the lemongrass with the back of a knife and cut into pieces. Slice the galangal, quarter the mushrooms and slice the chillies into rings.
Heat the coconut milk and stock in a saucepan. Add the lemongrass, galangal and makrut lime leaves and leave to infuse gently for a short while.
Add the mushrooms to the soup and cook for a few minutes until they are soft and have taken on flavour.
Add the prawns and cook only until they turn pink and are just cooked through.
Take the pan off the heat and stir in the fish sauce and lime juice. Season to taste until the soup tastes salty, fresh and rounded.
Ladle into bowls and serve with coriander and chilli. Traditionally, the lemongrass and galangal stay in the soup but aren't eaten.
Good to know
This soup is warm and clear in flavour, yet nicely creamy. It's on the table quickly and feels like a small dinner with a restaurant touch.
Swaps
Prawns → chicken breast (also plenty of protein). Galangal → ginger (similar spicy heat, easy to find). Fish sauce → tamari with a little salt (a soya-based alternative without fish). Mushrooms → shiitake (more umami, also contains fibre).
Allergens
Contains crustaceans and fish, plus soya if you use tamari; reduce the chilli a lot for children, and in pregnancy only use prawns that are fully cooked through.