Gaeng Som — Southern Sour Curry (No Coconut) / แกงส้ม

Ingredients

• For the paste
• 8–10 dried bird's eye chillies, soaked in warm water 10 minutes, drained
• 1 tsp dried turmeric, ground — not fresh
• 1 tbsp kapi (Southern Thai shrimp paste), deep-fermented; not substituted with milder pastes
• 4 cloves garlic, roughly chopped
• 3 shallots, roughly chopped
• 1 tsp salt
• 100 g tamarind block, extracted in 750 ml warm water, strained — not concentrate
• 600 g white fish — snapper, grouper, or platu (short mackerel), cut into steaks or large pieces
• 150 g green beans, trimmed, cut into 4 cm lengths
• 150 g cabbage or Thai eggplant, cut into bite-sized pieces
• 3 tbsp fish sauce, plus more to adjust
• 1 tsp dried chilli powder, to adjust heat at the end
• 2 tbsp neutral oil

Method

1. 1
   Pound the dried chillies, dried turmeric, salt, garlic, and shallots together in a mortar until a rough paste forms, adding the salt early so it acts as an abrasive and breaks the fibrous chilli skins down faster. Add the kapi and continue pounding until the paste is cohesive and the shrimp paste is fully incorporated. The paste should be uniformly deep gold and pungent — no large fragments of chilli skin remaining.
2. 2
   Soak the tamarind block in 750 ml warm water, working it with your fingers until fully dissolved, so the pulp releases all its sourness into the liquid rather than staying locked in the fibres. Strain through a sieve, discarding the solids. Reserve the tamarind water.
3. 3
   Heat the oil in a wok or wide saucepan over medium-high heat. Add the paste and fry, stirring constantly, for 1–2 minutes — this is where the raw edge is driven off and the kapi, which would otherwise dominate the finished broth aggressively, settles into a rounder, toasted fragrance. The paste is ready when the raw garlic smell has gone and that sharper note from the shrimp paste has softened.
4. 4
   Pour in the tamarind water and bring to a boil, then season with fish sauce. Add the green beans, cabbage, or eggplant — whichever vegetables are used — before the fish, because they need the full simmer time to become tender without the fish being present to overcook alongside them; simmer for 4–5 minutes. The broth should be visibly acidic and golden, and the vegetables should be tender but not collapsing — test with the point of a knife.
5. 5
   Add the fish. This is where the dish lives or dies: the fish must go in during the last 10 minutes only, and the heat reduced to a steady simmer immediately, so the flesh cooks through gently and holds its structure rather than flaking apart in the broth. Snapper or grouper should be just opaque to the bone — it will continue cooking in residual heat once off the fire, so pull it a moment before it is entirely done.
6. 6
   Taste and adjust. The sourness — corrected with additional tamarind water, never lime, which would give a different and sharper character — must be bold and forward; the heat, adjusted with dried chilli powder, is the cook's decision; fish sauce corrects the salt. The finished broth should read sour-dominant, then hot, then savourily deep. Serve immediately.