Take a full hisla fish and make medium pieces of it.

Take the mustard paste in a small utensil with a lid which can be put inside pressure cooker.

Add the oil.

Mix in the chopped onions and the green chillies and mix nicely.

Put the fish pieces and coat them with the mixture.

Close the lid of the utensil and place it in the cooker.

Close the lid of the cooker and place it over flame.

After one whistle, put off the flame.

Let the pressure release by itself.

:- The steamed hilsa is ready to be served.