Cut the fillets in about 4cm size.
Rub the fish well with the 1/2 tsp of turmeric and 1/2 tsp of salt and set aside for 10-15 minutes.
Heat the oil in a non-stick frying pan over a medium flame. If you are using mustard oil, let it get smoking hot.
Now put in the fish pieces and brown lightly on all sides without cooking them through.
Gently lift the fish out of the oil and put it on a plate. Turn off the heat.
Combine the ground coriander seeds, the cumin, ginger, 1 tsp turmeric,chilli powder (cayenne pepper) and 1/2 tsp of salt in a small bowl. Add 3 tbsp of water and mix.
Remove all but 5/6 tbsp of oil from the frying pan. Heat the frying pan over a medium flame.
When hot, put in the nigelia seeds. A few seconds later, put in the red chillies.
As soon as they darken a bit, put in the bay leaves. When the bay leaves start to darken, put in the onion.
Stir and fry the onion, lowering the heat, if necessary, until it is translucent and lightly browned. Add the spice paste. Stir and fry it for about 1 minute.
Now put in the fish in a single layer as well as 1 cup of water. Lay the green chillies over the fish.
Simmer over a medium heat for 2 minutes, spooning the sauce over the fish pieces as you do so. Now cover, turn the heat to low and
cook the fish for 10-15 minutes or until it is just done.
Serve machher jhol (fish in bengali sauce)with rice.