Toast the cloves and the coriander and cumin seeds in a small dry pan for 1 minute. Remove and grind the spices to a powder in a pestle and mortar or a small food processor. Tip into a small bowl and add the turmeric, garlic, ginger, white wine vinegar, salt and sugar. Set aside. In a large frying pan, heat 2 tbsp of the vegetable oil and add the onions. Fry for 5 minutes until golden. Add the spice mix and stir for 2 minutes. Add the tomato and cook until all the liquid has evaporated. Stir in the coconut milk and add 100ml water. Add the chillies and simmer for 15 minutes until the sauce has thickened. Add the fish and prawns and simmer for 5-7 minutes until cooked. Meanwhile, heat the remaining oil in a small frying pan. Add the mustard seeds and curry leaves. When the mustard seeds begin to pop, stir into the fish curry. Garnish with fresh coriander and serve with rice.
