A Fischbrötchen or Fischsemmel (lit. fish bun) is a sandwich made with fish and onions, sometimes also made with remoulade and pickles. It is commonly eaten in Northern Germany, due to the region's proximity to the North Sea and Baltic Sea.The most common preparation is made with bismarck herring or soused herring. Other varieties use Brathering, rollmops, European sprat, salmon, smoked Atlantic mackerel, other fried fish varieties (e.g. fish burgers).