Soak Emami Healthy & Tasty Mantra Shorshe Posto in warm water for about 8 minutes.
Grind it with 1 green chilli, yoghurt, grated coconut, and a little salt into a smooth, thick paste. Set aside.
Marinate the fish with turmeric powder and salt. Keep it aside for 10–15 minutes.
Heat oil in a thick-bottomed pan on medium heat. Once hot, add kalonji and the slit green chilli. Let it splutter.
Add the paste made at the beginning to the pan. Mix in turmeric powder, red chilli powder, and salt. Sauté for 6–7 minutes until the oil begins to separate.
Add 1 cup of water and bring it to a boil. Adjust salt and add sugar.
Now, slowly slide in the marinated fish and cook for 7-8 minutes on medium heat. Simmer till the sauce thickens.
Serve hot with steamed rice.