Tom Yum Soup

Tom yum is the iconic Thai soup of contrasts: hot from chili, sour from lime, salty from fish sauce, sweet from a touch of palm sugar, and aromatic from a galangal-lemongrass-kaffir lime spine that no other ingredient can substitute. The technique is layered. Bruise the lemongrass and tear the lime leaves to release oils; simmer them with galangal, garlic and chilies in stock for ten minutes to extract flavour, then strain. Return the broth to the pot, add fish sauce and lime juice off the heat — boiling lime juice turns it bitter — and finish with prawns or fish, cooked just to opaque. Acid and salt are added last, by taste.