Heat the mustard oil in a pan until it is hot enough and a faint haze rises.

Add the fish pieces one by one to the hot oil. Make sure you pat the fish pieces dry before putting them in the hot oil.

Fry them on both sides for 2 to 3 minutes per side until they turn golden brown. (Pro Tip: I do not flip the fish too early. Letting one side brown first makes it easier to handle).

Remove the fried fish pieces from the pan.

Add the whole cumin seeds, then add the chopped tomatoes and onion-ginger-garlic paste in the remaining hot oil. Give them a good stir. Cook for about 5 to 6 minutes until the tomatoes soften.

Then, add all the powdered spices (remaining turmeric, red chili, Kashmiri red chili, coriander, and cumin powder) and a little 1 tsp of salt. (Pro Tip: I keep the flame moderate while frying the spices so they cook evenly without scorching).

Stir for 2 to 3 minutes. Add half a cup of warm water and mix well.

Then add 1 cup of warm water for the gravy. (You can use about ½ cup water for a thick masala, 1½ cups for a curry).

Once the water comes to a boil, add the fried fish gently to the cooking pan.

Cover the pan with a lid.

Dry-roast 1 tbsp of cumin seeds in a pan for 1 minute, then grind. Add the cumin powder and the 3 pieces of green chilies.

Let the gravy simmer for about 5 to 7 minutes. Check the fish pieces with a fork for doneness. If done, then sprinkle coriander leaves and turn off the gas.

Fish masala is ready to be transferred to a bowl.