Smørrebrød, which means buttered bread in Danish, is an open–faced sandwich. Little squares (or triangles as the case may be) of dense, buttered rye bread are topped with a variety of seafood, meats, and cheeses often in combination with dill, onions, capers, and other herbs and vegetables.
Lynda Balslev, reporting for NPR, describes smørrebrød’s origins:
Denmark’s smørrebrød custom became entrenched with the onset of industrialization in the 19th century. Factory workers were no longer able to return home for a midday meal, so they packed a lunch of open–face sandwiches, which in their simplest form included slices of rugbrød (dense, dark rye bread) smeared with butter or animal fat (which helped to prevent the juices from seeping into and softening the bread), topped with cold meats, smoked fish or leftovers from dinner the night before. This tradition took hold over time, moving into the Danish mainstream. Families cultivated hand–me–down recipes, restaurants served more elaborate and creative variations, and the open–face sandwich secured its place at the holiday table.