Place the garlic, chillies, and ginger together in a food processor and process until smooth.
Heat the oil in a frying pan or wok and fry the onion with the curry leaves for four minutes over a medium heat.
Stir in the garlic, chilli and ginger mixture with the turmeric and salt. Fry for two minutes, then add 100ml/3½fl oz coconut milk with 155ml/6fl oz boiling water.
Simmer for two minutes and then add the fish pieces and gently simmer for 5-6 minutes.
Add half of the tomato and the remaining coconut milk and simmer for 3-4 minutes.
Garnish with the remaining chopped tomato.
Serve with basmati rice.
