Wash the fish well and pat dry
Add the onion, ginger, yoghurt, turmeric, salt, chili powder, chilis and 2 tablespoons of mustard oil and rub well
Keep the fish aside for around 15-20 minutes
Heat 2 tablespoons of the oil and let it smoke. Lower the flame and add the whole spices
Add the marinated fish into the flavoured oil
Add 1 cup of water and swirl the pot around so that the water spreads evenly in it
Cover and cook. After 5-7 minutes flip the fish pieces and again cover and cook. It should be cooked in 15-20 minutes
Serve the doi maach (Bengali fish curry with yoghurt) hot with steamed rice and some fresh salad. Bon apetit!