In a bowl of fish, add a tsp of red chilly powder, 1 tsp of turmeric powder, rock salt, 1 tbsp of refined oil. Gently massage the fish and keep it aside.
In a pan, heat 4 tbsp of mustard oil. Add 5 - 6 bedaki chillies, 1 chopped ginger, 6 - 7 garlic cloves, 1 tsp of coriander seeds, 1 tsp of cumin seeds and mix well for 2 min.
Put this masala in a mortar and pestle and grind it to a coarse paste.
In another pan, heat 5 tbsp of mustard oil and pan fry the fish till it becomes opaque/brown in color. Take out the fish and keep it aside.
In another pan, add the hot fish flavored mustard oil. Put 1 bay leaf, 1 cinnamon tick, 1 cup of finely chopped onions and mix it well.
Add 3 slit green chilies and mix well.
Add the coarse spices into this aromatics mixture and keep stirring. Add a tsp of turmeric powder, 1 tsp of red chillies, ½ tsp of sea salt and keep on sauteing it till it becomes red chilly in color.
Add water if necessary to combine all spices till the oil separates.
When the oil has separated, add a cup of whipped curd and mix it well for 5 - 10 minutes. Add water and bring it to boil.
Add sugar and a dash of lime juice to balance the flavor. With the help of a whisker, whisk the masala.
Put the poached fish in this gravy along with the resting juices of the fish.
Cover the lid and let it simmer for 5 - 7 min, till the gravy thickens.
Serve hot with steamed rice.