Well, living close to Denmark we eat a lot of open sandwiches on rye bread. My favourite toppings are eggs and pickled herring with chives. Egg and shrimps with mayo, dill and lemon. Fried breaded plaice with remoulade sauce. Fried eggs and sausage.
We also have The Bestest Sandwich Ever!!! Sandwich cake

. Big slices of white bread, layered like a cake with different fillings between like chopped eggs or cured salmon or shrimps or crab sticks mixed with seasoned mayo and crème fraiche. Then the cake is artfully decorated with vegetables and shrimps, cured salmon, cheese, ham, thinly sliced roast beef or similar.
A smaller version is a gang plank, a long thin sandwich starting from “the ocean” to land. Cured salmon, shrimps, eggs, cheese, ham, roast beef and suitable vegetables and sauces

. It’s to be eaten from ocean to land too…
