Walk into any Bengali kitchen, and you will find the larders stocked with a jar of coarse, white poppy seeds. Known as posto in Bengal and khus khus elsewhere in India, this byproduct of the narcotic opium poppy plant has been ruling Bengali hearths and hearts for the last two centuries.
A typical Bengali meal is multi-course, with rice accompanying each dish. “Vegetables, especially the bitter ones, are the first item, followed by dal, perhaps accompanied by fries or fritters of fish and vegetables,” writes Chitrita Banerji in her book Bengali Cooking. “After this comes any of the complex vegetable dishes like ghanto or chachchari, followed by the important fish jhol as well as other fish preparations. Meat will always follow fish, and chutneys and ambals will provide the refreshing touch of tartness to make the tongue anticipate the sweet dishes.” Posto is the go-to ingredient for Bengalis to add a nutty taste and a grainy texture, as well as thickness, to nearly all these dishes.
Traditionally, home cooks soak raw poppy seeds in water for over an hour before grinding them with a stone slab and pestle called a “shil noda.” The resulting paste is posto bata. The creamy (though slightly grainy) and nutty posto bata is enhanced with pungent mustard oil, chopped green chilies, and a pinch of salt; the resulting blend can be consumed as a dip or chutney. Cooks can add it to meat, fish, and vegetable curries to thicken the gravy. Cooked with potatoes and kalo jeera (nigella seeds), the paste becomes the savory aloo posto, a common Bengali comfort food. Today, it is even used in sweets.