Wash and clean prawns (please check notes for further details).
Marinade the prawns with salt and turmeric powder and leave those as it is for 10 minutes.
Soak Mustard Seeds in hot water for 15 minutes.
Add ½ Tsp. salt to it while soaking.
Make a paste of the mustard seeds and add little water to make it diluted.
Strain the Mustard seed paste and discard husk.
Make a paste of the scrapped coconut as well.
Now take Mustard Seed paste, Coconut paste, and Plain curd in a bowl and beat using a spoon.
Add Salt and Turmeric powder to the mixture.
Add 3 tablespoon Mustard oil is also followed by slit green chilies.
Mix everything.
Now marinade the prawns with the paste for 15 minutes.