In a mixing bowl take the pieces of Hilsha and clean it with running water.
Then take the fish pieces and marinate it with turmeric powder and salt and mix it well and keep it aside.
Cut the brinjal into slices and wash it properly.
Then take a kadai or a pan heat it and pour 4 table spoons of mustard oil in it and put the fishes into it. Fry the fishes but it shouldn’t be too much fried as hilsa will loss it’s own taste. After frying take the fishes into a bowl and keep it aside.
Again pour 1 table spoon of mustard oil into the same kadai and put the brinjal into and fry it lightly. Drain the exece oil from it and keep aside.
Then add oil in the karai and then heat it and put the black cumin / kalonji in the oil along with few slitted chillies as it gets automatic put along with all the dry spices as (cumin powder, coriander powder , red kashmiri mirch powder and a bit of turmeric powder and few crystal of sugar just to enhance the flavour and taste of the gravy ). cook it for 2 mins as it releases the oil from the masala pour ½ cup of Luke warm water just to ensure the masalas not to get burn.Mix it well.
Now put the brinjal and properly mix it with the masala along with amount of salt as needed . Then pour rest of the water according to the amoun of your gravy ,let it come for a proper boil in it as the oil starts floating above put the fried fish pieces into the kadai and let it be boiled for 5 minutes. Make sure the fish pieces dose not break .