-
1
Combine the lime juice, fish sauce, palm sugar, pounded garlic, sliced chillies, and pounded coriander root in a bowl, stirring until the palm sugar dissolves completely. Set the dressing aside for 10 minutes so the garlic and chilli have time to perfume the lime juice rather than sitting raw on top of it. The dressing should smell immediately sharp and bright — the volatile oils of fresh lime are fully present.
-
2
Bring the steamer to a full, vigorous boil before the fish goes in, so the flesh seizes immediately and stays moist rather than stewing in slowly rising steam. Place the lemongrass stalks and kaffir lime leaves inside the cavity, set the fish on the steamer tray, and steam over high heat for 10–15 minutes with no oil or seasoning on the skin. At 10 minutes, insert a metal skewer behind the pectoral fin — it must slide through with no resistance — then pull the pectoral fin: the flesh along the backbone must be just opaque, not translucent; if any translucency remains, continue for 2 more minutes and re-test.
-
3
Transfer the fish to a warmed serving plate, then ladle one tablespoon of the steaming liquid that has accumulated in the steamer tray directly over the fish, so that condensed, fish-flavoured stock adds depth before the dressing goes on. This is where the dish lives or dies: immediately pour the cold dressing over the entire surface of the hot fish, because the temperature difference causes the lime's volatile oils to vaporise at once, filling the air above the plate with fresh citrus and fish sauce in an aromatic event that lasts no more than 10 seconds. The fish must be plated and the dressing poured without delay.
-
4
Scatter coriander leaf and sliced spring onion over the fish and serve at once. At the table, the first combined taste should register clean sweetness from the fish, bright acid from the lime, salt from the fish sauce, and building heat from the chilli — each distinct, none dominant.