Clean and cut 500 g of any fish / prawns into square or round pieces and keep aside. In a wide, thick-bottomed vessel (clay or non-stick), pour three to four tablespoons of coconut oil.

Keep the following ready for sauteing:
Ginger - 2 inches (slice into thin, long pieces)
Garlic - 10 to 12 cloves (slice into thin, long pieces)
Shallots - 5 to 6
Curry leaves - a few

Splutter a teaspoon of mustard seeds, add the above four ingredients and saute.

Then add a paste made of the following:
Kashmiri chilli powder  - 4 to 6 tsp  
Fenugreek powder - ½ tsp  
Turmeric powder - ½ tsp  

The masala or paste can be made either by grinding the three powders together or adding little water to the powder mixture. Stir till the oil separates from the masala. Add salt to taste, few pieces of tamarind (cocum) and half to one cup of water. Let it boil. Then, arrange the slices of fish neatly in the boiling masala with some curry leaves on top. Cover and cook till the fish are done and the gravy becomes thick. Then, add three tablespoons of coconut oil on top and remove from the fire. Keep this fish curry for 10-12 hours before using it. One may use it immediately after it is done but the taste will not be as good.