Simmer 450g of boneless, skinless chicken thighs, cut into 1in / 2.5cm pieces, in 2 cups of unsalted chicken stock with ½ teaspoon of salt for about 15 minutes.
Add 1½ cups of coconut milk, 1 lemongrass stalk, bottom half smashed and cut into pieces, 12 thin slices of galangal, 5 torn makrut lime leaves, 2 Thai chilies, and 155g of oyster mushrooms, torn.
Stir in half of 2 tablespoons of fish sauce and 1 teaspoon of chopped palm sugar. Simmer for about 5 minutes.
Turn off the heat. Stir in most of 2½ tablespoons of lime juice, then season to taste with the remaining fish sauce and lime juice.
