Rui Posto is a classic Bengali fish curry made with Rohu fish cooked in a rich and creamy poppy seed paste. The fish is marinated with turmeric and salt, then pan-fried until golden. The curry is prepared by grinding poppy seeds with green chilies and mustard oil to form a smooth paste. The paste is then cooked with spices like turmeric, red chili powder, and cumin powder. The pan-fried fish is added to the curry and simmered until cooked through. Rui Posto is best enjoyed with steamed rice.