Wash and pat the fish chunks dry.
Sprinkle them with 1 teaspoon of salt and 1 teaspoon of turmeric powder.
Marinate the fish and let it sit for 10 minutes before frying.
In the meantime, finely chop one onion and one tomato. Also, cut two green chilies in half.
Heat 8 tablespoons of mustard oil in a pan, wok, or Kadhai.
While you can fry fish with less oil, I use extra oil and then use the leftover oil in other dishes.
Heat the oil until its color changes.
Begin frying the fish chunks. Keep the flame high, fry one side for 30 seconds, then flip and fry the other side.
Continue this process for the remaining fish.
I use extra oil for frying. Once done, I leave 3 tablespoons of oil in the pan to make the curry.
The rest of the oil is flavored with chili and saved to serve with rice.
To prepare the curry, temper the remaining 3 tablespoons of oil in the pan with 1 teaspoon of nigella seeds (also known as Kalojire or Kalonji).
Add the green chilies to the tempered oil.
Now, add the chopped onion and stir constantly.
Cook on medium heat until the onion changes color.
Then, add the chopped tomatoes and mix.
Once the tomatoes soften, add 1 tablespoon of garlic paste.
Mix continuously and cook for 2 minutes. Finally, add ½ teaspoon of turmeric powder and 1 teaspoon of teaspoon of sugar and half a teaspoon of salt.
Stir and cook for another two minutes, adjusting the spices if necessary.
Once the mixture starts releasing oil, add one-third cup of water and mix well.
Continue cooking until all the water has evaporated. You'll notice the oil has a beautiful red color and the tomatoes are completely soft.
Now, add two cups of water and bring it to a boil.
As soon as it boils, add the fried fish. Mix thoroughly and cook on medium heat until the sauce thickens.
This should take about five to six minutes to cook perfectly.
I prefer this consistency for Macher Rosha, but you can make it thinner and, of course, omit the sugar.
While Macher Rosha pairs wonderfully with rice, you should definitely try it with Roti at least once!