Heat 3 tsp of oil; add whole garam masala, red chilli, chopped ginger & garlic, chopped onion fry for 5 min, add chopped tomato cook for 5 min. Now add grated coconut, salt grind as smooth paste.
In a bowl take cleaned prawns add turmeric& ginger-garlic paste mix well & marinate for 30 min.
Now heat 4 tsp of oil; add shahijeera, cumin seeds, mustard seeds saute it, add the prepared masala paste fry for 5 min.
Now add the marinated prawns & cook for 15 min on medium flame.
Finally sprinkle the coriander leaves & serve hot with rice or roti.