1. Marinate 200 gms fish pieces with 1/2 tsp salt, 1/2 tsp turmeric powder and 1/2 tsp red chilli powder for 10 minutes.
2. Meanwhile soak 1/2 cup mustard seeds in some water for 10-15 minutes.
3. Make a paste of mustard seeds by adding 2 green chillies and 1/4 cup of water in mixture grinder.
4. Make a paste of 1 large tomato with 4-5 garlic pods. keep it aside.
5. Heat some mustard oil in pan, fry the fish pieces in batches for 3-4 minutes from both the sides. keep it aside.
6. In the same pan, add some more mustard oil, add 3 dry red chillies, 1/2 tsp each of mustard seeds, onion seeds / nigella seeds / kalonji, fennel seeds / saunf, fenugreek / methi seeds, 7-8 curry leaves and cook it for 1 minute.
7. Add the tomato and garlic paste and cook it for well for 3-4 minutes on a medium flame.
8. Lower the flame, add 1/2 tsp turmeric powder, 1 tsp red chilli powder, 1/2 tsp cumin powder and salt to taste. add few splashes of water and cook it further for 4-5 minutes.
9. Next add 4 tsp of mustard seeds paste and cook it for 1-2 minutes.
10. Add around 1 cup of warm water, 2 slit green chilies. once the gravy starts to boil, add the fried fish pieces, cover and cook it for another 3-4 minutes on a medium flame.
11. Lastly add around 1 tsp of lemon juice and few chopped coriander leaves.
12. Mix it well, switch off the flame, cover and rest it for 2 minutes and its ready to be served.
1. We will not be required to use all the mustard paste, just 4 tsp would be enough. you can store the remaining mustard paste in refrigerator for later use.
2. Generally, more oil is required to fry the fish pieces, you can use the same oil to make the gravy.