Salted herring fillets soaked, then kept in a sweet-sour pickle of vinegar, sugar, onion and whole spice.
Herring shoaled in huge numbers in the Baltic and the North Sea, and salting it was a trade that helped make the Hanseatic towns rich. Salted, it kept through the winter; pickled in vinegar and sugar, it became the centre of the cold table.
Every Nordic Christmas and midsummer table has several kinds — in mustard sauce, with dill, in curry cream — eaten on rye bread or with boiled new potatoes, and a glass of something cold.