Heat the sunflower oil in a large casserole dish over a medium heat until hot. Sweat the onion, garlic and ginger for 8-10 minutes, stirring occasionally until the onion starts to soften.
Add the ground spices, chilli powder, turmeric, a pinch of sugar and some seasoning, stir well and cook for a further 1-2 minutes. Stir in the tomato puree, cook for 1 minute, stirring occasionally, then add the chopped tomato and the chunks of fish.
Cover with the fish stock and coconut milk, stir well then bring the mixture to a simmer. Simmer for 10-12 minutes until the fish is just cooked. Adjust the seasoning to taste, then spoon the soup into serving bowls. Garnish with coriander leaves before serving.
Freezing and defrosting guidelines
You can freeze the soup at the stage before adding the fish. Cook as instructed and allow to cool completely. Then transfer to an airtight, freezer-safe container, seal and freeze for up to 1-3 months. To serve, defrost thoroughly in the fridge overnight before reheating. To reheat and serve, place on medium heat, adding the fresh fish and simmering until the fish is cooked. Coconut milk can be used before freezing but taste the best when served fresh.