Kæstur hákarl is a national dish of Iceland consisting of a Greenland shark (Somniosus microcephalus) or other sleeper shark which has been cured with a particular fermentation process and hung to dry for four to five months. Kæstur hákarl has a strong ammonia-rich smell and fishy taste.

Kæstur hákarl is readily available in Icelandic stores and is eaten year-round, but is also served as part of a þorramatur, a selection of traditional Icelandic food served at þorrablót in midwinter. (source)