Clean and cut fish fillet, wash well, remove excess water and then marinate with limejuice, turmeric powder and salt. Keep aside for 30 minutes.
Heat up a pan, mix in 1 tbsp oil, shallow fry marinated fish from both sides until slightly browned. Take off and keep aside.
Heat up remaining oil, mix in mustard seeds, kalonji, whole dry red chillies and bay leaf, stir fry for a few minutes till seeds crackles, mix in ginger, garlic paste and stir fry again for a moment. Mix in cut onion and stir fry until slightly brown in colour. Mix in mustard paste, red chilli powder, coriander powder and turmeric powder, stir fry masala nicely until oil starts separating. Adjust water and salt, bring to boil and then mix in shallow fried fish, put green chilli slits on top. Stir fry on a slow flame until fish get cooked and oil starts floating on top of gravy.
Take off and decorate with cut green coriander leaves. Serve with rice.