Wash the fish under running water and then pat them dry. Marinade the fish pieces with salt and 1/2 tsp turmeric powder and leave for ten minutes.

In the meanwhile, make a paste of the onion in a blender using very little water.

In a frying pan or a kadai, take, 2 tbsp of mustard oil and let it heat. When smoking, gently slide the fish pieces and put the flame on medium. The fish should be lightly fried Just a little bit of colour on one side and then it's time to flip the fish on the other side. Once both sides are done, take the fish out of the oil using a slotted spatula and keep aside.

In the same oil, add another tbsp of mustard oil and let it heat. Add the onion paste and kep frying. After a couple of minutes, add ginger paste and continue frying.

Take both mishti doi and normal yogurt in a mixing bowl. Add a tsp of maida or all purpose flour and whisk thoroughly, till there are no lumps and keep aside.

Add 1/2 tsp of turmeric powder and the kashmiri red chili powder and continue frying. Sprinkle some water if the masala starts to stick to the bottom.

Continue frying till oil starts to show around the sides. At that point reduce the heat to a minimum and add the whisked yogurts.

Keep stirring or else the yogurt will split. After a minute or two, add a cup of water and stir well. Then you need to slowly increase the heat and let the gravy cook and the raw smell of the yogurt should go in a while.

Slide the fish pieces in the gravy and check the seasoning. Add the split green chilies and increase the temperature. Adjust the water as per your liking.

The sauce should continue simmering for a while till you can see oil floating on top. That's from the yogurt.

Turn off the heat and serve doi maach with steamed rice.