Kaeng Som

Central Thai sour fish curry: an austere, fiercely sour broth of dried chilli paste and tamarind with fish and seasonal vegetables, served over jasmine rice

Origin: Central Thailand

From the journey of Chilli Pepper.

Kaeng som (แกงส้ม), literally sour curry, is one of the oldest and most widely eaten curries of central Thailand: a clear, intensely sour and spiced broth built on a dried chilli paste base and sharpened primarily with tamarind, containing fish or prawns and seasonal vegetables. It stands apart from virtually every other Thai curry. There is no coconut milk, no warm spice blend, no richness or creaminess to moderate the heat or the sourness. Kaeng som is defined by its austerity and its acidity; where massaman is built for the comfort of long-braised richness and kaeng khiao wan for the perfumed freshness of green chilli and basil, kaeng som makes no concessions. The curry paste for kaeng som is deliberately spare: dried red chillies, shallots, and fermented shrimp paste (kapi), with turmeric added in the southern Thai version, which carries the alternative name kaeng lueang (yellow curry). The broth is water-based, brought to a simmer and seasoned with fish sauce. The sourness arrives from two directions: tamarind water, which is the classical and primary souring agent throughout the central Thai tradition, and cherry tomatoes, a Bangkok adaptation in which the tomatoes are added with the vegetables to contribute both an additional layer of acidity and a brightness of colour that rounds out the tamarind's deeper, darker sourness. The protein is invariably fish or prawns: whole fish fillets or firm white fish such as sea bass or tilapia, or large raw prawns. Pork and chicken are not traditional in the central Thai version; the clean, marine character of fish or shellfish suits the sharpness of the broth. Vegetables vary by season: white radish, pak choi, green beans, and Chinese cabbage are the most common. Kaeng som is served ladled directly over steamed jasmine rice, with fresh raw cucumber or spring onion alongside to cool the palate against the broth's assertive heat.

Ingredients

Curry Paste

  • 8 large dried red chillies, stems and seeds removed, soaked in warm water for 10 minutes and drained
  • 4 shallots (approx 80g), peeled
  • 1 tsp kapi (Thai fermented shrimp paste), dry-roasted in a dry pan for 30 seconds per side, or wrapped in foil and grilled
  • 0.25 tsp ground turmeric (for colour; traditional in the southern version, optional in the central)
  • 0.5 tsp fine salt

Broth

  • 1 litre fish stock, or water
  • 3 tbsp tamarind water (2 tbsp tamarind paste dissolved and strained from 4 tbsp warm water)
  • 2.5 tbsp fish sauce (nam pla), plus more to taste
  • 1 tsp palm sugar or light brown sugar

Protein and Vegetables

  • 400 g firm white fish fillets (sea bass, tilapia, or snapper), cut into 3cm pieces; or 300g large raw prawns, peeled and deveined
  • 150 g white radish (daikon), peeled and sliced 1cm thick
  • 100 g green beans, trimmed and cut into 4cm lengths; or 1 small pak choi, separated into leaves
  • 100 g cherry tomatoes, halved

To Serve

  • To serve: steamed jasmine rice, fresh cucumber sliced, spring onion trimmed

Method

  1. Make the tamarind water: place the tamarind paste in a small bowl, add 4 tablespoons of warm water, and work the pulp with your fingers to dissolve it fully. Strain through a sieve, pressing the solids firmly to extract all the liquid. Discard the fibres and seeds. Set aside.
  2. Pound the curry paste: in a mortar, pound the drained soaked chillies with the salt until broken down. Add the shallots and dry-roasted kapi; pound until a smooth, cohesive paste forms. Stir in the turmeric. Alternatively, blend in a small food processor with 2 tablespoons of water to help the blades move.
  3. Bring the fish stock (or water) to a steady simmer in a medium saucepan. Add the curry paste and whisk to dissolve it completely into the broth. Simmer for 3 minutes.
  4. Add the tamarind water, fish sauce, and palm sugar. Stir well and taste: the broth should be simultaneously sour, salty, and hot, with a clear, clean flavour. Adjust with more tamarind water for sourness or fish sauce for saltiness.
  5. Add the white radish. Simmer for 5 minutes until just beginning to soften.
  6. Add the fish or prawns, green beans or pak choi, and cherry tomatoes. Simmer for 3 to 4 minutes until the fish is just cooked through and the vegetables are tender but retain a little bite. Do not overcook the fish.
  7. Taste once more and adjust the seasoning. Ladle directly over steamed jasmine rice in deep bowls. Serve with sliced cucumber and spring onion alongside.

Notes

Tamarind is the primary souring agent in kaeng som; cherry tomatoes are an addition of the Bangkok and central Thai adaptation that adds brightness and co-acidity. In the more austere traditional version, the tomatoes are omitted entirely and the full sourness comes from tamarind alone. For the southern Thai version (kaeng lueang, yellow sour curry), increase the turmeric to 1 teaspoon and substitute pineapple chunks for some or all of the white radish, adding them with the fish. Kapi is essential to the depth of the paste; without it the broth will taste thin and one-dimensional. Both fish and prawns work well in the same recipe; if using both together, add the prawns 2 minutes after the fish as they cook slightly faster.

The Gastrographer

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