Make a fine paste of the black mustard seeds, grated coconut, a little salt, and 2 pieces of green chilies. (Pro tip: It is better to use both black and white mustard seeds in equal proportions for a better flavor and less pungency.)

Take the mustard paste in a separate bowl and then add the turmeric powder, Kashmiri red chili powder, and 1 tbsp of mustard oil and some more salt to taste. Mix well.

Marinate the hilsa fish pieces by coating with the spice mix. Keep them aside for 10 minutes. (Pro tip: Coat the fish pieces evenly on both sides with the paste for the best and authentic taste and flavor).

Place each piece of fish on a separate banana leaf and add a little bit of mustard oil, one green chili, and one red chili on it. Repeat the same process for the other pieces of fish.

Wrap the fish pieces with the banana leaf, ensuring that it is fully covered. Use a cotton string to tie the parcel firmly.

Preheat a tawa on the gas stove and heat the remaining mustard oil.

When the oil is hot, place all the banana leaf wraps side by side on the tawa and cover it with the lid.

Once one side is cooked, flip the banana leaf wraps and cook the other side.

Steam the banana leaf wraps for 5 minutes on each side. You can place a lid on the pan.

Ilish Paturi is ready. Unwrap the banana leaf and serve.