Place the soaked chillies, paprika, curry powder and coconut in a food processor with the coconut milk and blend to a smooth paste.
Transfer the spice paste to a wide saucepan, add the measured water, stir to mix well and bring to a gentle simmer over a medium-low heat. Add the tamarind paste, green chillies, ginger and onion, and season to taste. Stir and simmer for 2–3 minutes.
Add the fish to the pan, stir once, cover and simmer gently for 10–15 minutes until the fish is just cooked. Serve hot with steamed rice.