Lightly bruise chili using the side of your knife.
Put coconut milk, chicken, galangal, straw mushrooms, chili, lemongrass and kaffir lime leaves into a pan over medium-high heat. Bring to a low simmer and simmer (do not boil) for 4–5 minutes until chicken is cooked.
Remove from heat and add fish sauce and lime juice. Taste. Add more flavouring to suit. Serve garnished with coriander leaves and spring onions.