A traditional Bengali preparation of prawns cooked in mustard and filled inside a coconut to get a combined flavor of mustard and coconut cream.
1. Take a tender coconut (green coconut) which has started to form soft layers of coconut inside. Make a whole (2x2 inches) on the top keeping the cutout to use as a lid later. Drain out the coconut water inside into a separate bowl and keep the coconut aside.
2. Make a paste of onion, garlic, ginger, green chilies and tomato
3. Remove the prawns from shells and marinate with salt, turmeric powder and mustard oil(1 table spoon)
4. Make a semi liquid paste of 3 tablespoon of mustard powder (home made mustard seed paste would be recommended) with coconut water (3-4 tablespoons).
5. Cook the marinated prawns for 2 minutes in microwave and keep aside.
6. Heat oil(2 table spoon) in a pan. Add paste of onion, garlic, ginger, tomato and green chili
7. When the paste well cooked and all the water is released (approx 5 minutes), add the semi-liquid mustard powder paste and cook for 2 minutes
8. Add the microwaved prawns and cook till the gravy is thick.
9. Pour the entire content of the step in the coconut, and then add 4 cut green chilies.
10. Cover the cut portion of the coconut with the coconut lid.
11. Put the coconut in the microwave and cook for 10-15 minutes.
12. Take out the lid of the coconut, check if the prawns are soft. If required may be cooked for 5 minutes more. Serve with rice.