Boal Machher Jhol

Smear the fish with salt and turmeric, and set aside for 15 minutes.Slice onions, dice tomatoes, slit green chillies, and crush garlic in a mortar-pestle.Heat a kadai on the stove. Once sizzling hot, turn down the heat and add mustard oil. Adding oil to a well-heated pan will develop a non-stick layer and ensure the fish doesn't stick.Fry the fish in batches, in a single layer, on all sides, until brown. This will take 4–6 minutes depending on the piece.Remove from the oil and set aside.Temper the same oil with cardamom, cinnamon and kaalo jeere.Add onions, and sweat them on low heat until light golden, about 12 mins. Make sure they don't brown. If they start to colour, splash some water to lower the temperature of the pan and arrest excessive browning.Add tomatoes, salt and sugar, and cook until the tomatoes soften.Add garlic and 2 slit green chillies, and continue frying for about 4 mins.Add the turmeric and red chilli powder. Cook until their raw smell dissipates, about 6 mins.Add Bengali gorom moshla and some atta (for a cohesive sauce).Add hot water for the sauce.When it comes to a boil, lower the fried fish.Simmer on gentle heat for 7–8 minutes. Turn off the heat and let it stand for a couple more minutes before serving.