Marinate the fish with salt and turmeric powder. Leave them aside for 10 minutes.
Add 4 tablespoons of mustard oil in the kadai (wok).
When the oil is hot, slide the fish pieces carefully.
After one side is done, flip the pieces and fry properly.
Take them out on a plate.
Add nigella seeds.
After the nigella seeds start splattering, add the paste and give it a good stir.
Clean the bowl and add the spice-loaded water to the pan.
Add salt and turmeric powder. Stir well.
Continue stirring for 2 minutes on low flame.
The paste will release oil. Add green chilies.
Add water as required.
After the water comes to a boil, add the fish pieces one by one.
Cover the pan with a lid.
After 5-7 minutes, turn off the heat. Take out the fish curry and serve with steamed rice.