Marinate the fish with salt, a pinch of turmeric powder and a few drops of mustard oil. Keep aside.
Soak the hing in 1 tbsp water, keep aside.
Heat 1 tbsp oil in a pan, shallow fry the fish till light brown. Keep aside on a kitchen absorbent towel.
To the same pan, throw in the kalonji and 2-3 green chilies, allow to splutter.
Add the chopped tomatoes, ginger juice, 3-4 green chilies, the remaining turmeric powder and salt. Cook till oil starts to release from the masala.
Add 1 cup of warm water. Bring to a gentle simmer.
Carefully place the fried fish in the curry, throw in the fried boris and the remaining green chilies, add the hing-water.
The curry shall not be too runny or too thick. Continue to cook for another 5-6 minutes till the consistency is right.
Finish with chopped coriander leaves. Serve hot.