Rinse 3 pieces of kudampuli (Malabar tamarind) and soak them in ¼ cup of hot water.
Heat 2 tablespoons of coconut oil in a wide pan. Sauté ¾ cup of sliced shallots, 1 piece of ginger, 1in / 2.5cm long, finely chopped, 4 large chopped garlic cloves, 2 slit green chilies, and half of 2 sprigs of curry leaves for 6-7 minutes.
Add ½ cup of chopped tomato and cook for 4-5 minutes. Stir in ½ teaspoon of ground turmeric, 2 tablespoons of Kashmiri chili powder, 1½ tablespoons of ground coriander, and 1 teaspoon of salt.
Add the kudampuli with its water, two-thirds of 270ml of canned coconut milk, and ¾ cup of water. Cover and boil for 3-4 minutes.
Add 500g of fish steaks, about 1in / 2.5cm thick, cover, and cook for 10 minutes. Add the remaining coconut milk and curry leaves and simmer uncovered for about 5 minutes, until the fish is cooked through.
