The heat doesn't come mainly from chili — it comes from chopped pieces of the chui vine's stem and root, which diners chew after cooking to release their sharp, peppery sap.
Chunks of a climbing pepper vine called chui — its peeled stem and root, not its fruit — are simmered for hours with beef or mutton until they turn tender and release a sharp, horseradish-like bite into the gravy. Khulna's markets and eateries treat it as the region's defining curry, distinct from anything found elsewhere in Bangladesh.