Grind the mustard, chilies, turmeric powder and coconut to a smooth paste. In a bowl, mix the paste along with the prawns, mustard oil, salt, yoghurt and coriander leaves.
Transfer it to a steel container with a lid. Pour some water in the pressure cook and place the closed steel container over it.
Steam cook without the vent for 15-20 minutes (10 minutes on high flame and the remaining on low flame). Serve on a bed of hot steamed rice.
