Cut the fish into 1.5inch cubes. (Avoid bony fish.)

Make a paste of 1 tsp of turmeric, 1 tbsp of chilli powder, 1 tbsp of coriander powder, 1 tsp of pepper powder, salt and juice of 1 lemon or 2 tsp vinegar.

Apply it on the cut fish and refrigerate for atleast an hour. This can be done a day before too.

Medium- fry the fish pieces and keep them aside.

Chop the onions and tomatoes into small pieces.

Grate the ginger and garlic and slit the green chillies.

Add the tamarind to 1/2 cup water.

Extract coconut milk so that you have one cup of thick coconut milk and two cups of thin milk.

Heat 2 tbsp of oil in a heavy bottom vessel with lid.

Splutter the mustard seeds in it.

Fry the onion till golden brown followed by ginger, garlic and chillies.

Add the tomato and fry till dry.

Add the chilli powder, coriander powder, masala and 2 tbsp water. Fry till the masala is fried(be careful not to burn it).

Add the two cups of thin coconut milk and the tamarind extract and cook covered.

When it starts boiling, reduce the flame.

Add salt and the fried fish pieces. Stir carefully so that the fish pieces do not break.

Cook covered for 5 minutes in the lowest flame. Turn off the flame.

Add the thick coconut milk and stir slowly.

Check the salt and spice. Add if necessary.

Garnish with curry leaves.