Kippers

A kipper is a whole herring, a small, oily fish, that has been split in a butterfly fashion from tail to head along the dorsal ridge, gutted, salted or pickled, and cold-smoked over smouldering wood chips . In the United Kingdom, Republic of Ireland and some regions of North America, kippers are most commonly eaten for breakfast. In the United Kingdom, kippers, along with other preserved smoked or salted fish such as the bloater and buckling, were also once commonly enjoyed as a high tea or supper treat, most popularly with inland and urban working-class populations before World War II.

Source: Wikipedia