Heat the stock in a saucepan over a medium heat until reduced by half.
Add the coconut milk and cream, the chicken, lemon grass, lime leaves and galangal. Simmer for 6-8 minutes until the chicken is cooked.
Add red chilli, if using, the lime juice and fish sauce, and remove the pan from the heat. Taste to check the seasoning, divide between bowls and garnish with the coriander. Serve with rice, and the extra chilli slices and lime wedges for squeezing over, if you like.