1 tbsp soft light brown sugar (add less if you don't want a sweet curry)
1 green chilli deseeded and finely sliced
500g firm white fish, skinned and cut into chunks
2 tbsp chopped coriander
Toast the coriander seeds, cumin and dried chillis in a dry frying-pan for about a minute. Grind in a mini food processor or pestle and mortar, then mix in the ginger, garlic, turmeric and 1 tsp salt.
Heat the oil in a sauté pan over a medium heat, then add the onion and fry until soft and golden. Stir in the spice mix. Cook, stirring, for a couple of minutes, then add the tomato and cook until it has lost most of its moisture.
Add the coconut milk, sugar, tamarind and green chilli and bring to just under the boil. Immediately turn down the heat and simmer for about five minutes, until the sauce has thickened slightly.
Taste for seasoning. Season the fish with salt, then add it to the sauce and simmer gently for about four minutes until the fish is cooked through. Check again for seasoning. Add the coriander and serve.