Tom Kha Gai

Method

1. 1Bruise the aromatics: smash the lemongrass stalks with the flat of a knife and cut into 5 cm lengths, slice the galangal into thin coins, and tear the kaffir lime leaves. This is what releases their oils into the broth — galangal, not ginger, is the defining flavour of tom kha.
2. 2In a pot, bring the chicken stock and about half the coconut milk to a gentle simmer with the lemongrass, galangal, and kaffir lime leaves. Let it infuse for 5 to 10 minutes so the broth takes on their fragrance.
3. 3Add the sliced chicken and poach gently until just cooked, about 5 minutes. Keep it at a bare simmer — a hard boil toughens the chicken and can split the coconut milk.
4. 4Add the mushrooms and the rest of the coconut milk and simmer for another 3 to 4 minutes until the mushrooms are tender.
5. 5Season off the heat, or at the lowest simmer, with the fish sauce and sugar. Add the whole or lightly crushed Thai chilies — crushing them releases more heat, leaving them whole keeps it gentle.
6. 6Stir in the lime juice last, off the heat. Adding it while the soup is boiling turns it bitter and dulls the fresh sourness that balances the coconut.
7. 7Taste and balance: it should be creamy, salty, sour, and mildly hot all at once. Adjust with more fish sauce, lime, or sugar, then serve scattered with cilantro.