Open sandwiches, or smorrebrod, are central to the Danish diet. They are usually made with rye bread, topped with butter, lard or poultry drippings, and any combination of meat, fish, pickles, vegetables and herbs. They can be had at any meal, or at any time in between. There is a 19th-century classic, curiously named the veterinarian's midnight snack, that consists mainly of pork liver pate, salt beef or pork and aspic. It is said to have come from the House of Davidsen, a famed Copenhagen restaurant. Oskar Davidsen was a wine merchant who expanded his business by opening a wine bar and shop in 1888. When the bar opened, there was no menu; when clients got hungry, his wife, Petra, would whip up a smorrebrod for them. The sandwiches became incredibly popular, however, and soon people were coming for Petra's snacks every lunchtime. The accidental success led the couple to change their focus to smorrebrod. Everyone had their favourite combination of toppings. One day, a veterinarian came into the restaurant asking for bread topped with liver pate, aspic and salt beef - a slightly unconventional mix as it involved so much meat. Some say the vet had made this once himself when he got home late one night and didn't have any other ingredients to hand. The restaurant obliged, and added onions and dill for extra flavour. The vet loved it so much that he became a regular, and the sandwich was named for him. After four generations of Davidsens and a move to new premises, the sandwich is still served at what has become the Restaurant Ida Davidsen. 1/2 slice of rye bread with butter 1 slice of pork liver pate 1 slice of flavoured lard 1 slice of consomme aspic 4 paper-thin slices of salt beef 3 onion rings 1 sprig of fresh dill For the flavoured lard: 250 grams lard 1 Granny Smith apple 1 onion 1 tbsp thyme To make the flavoured lard, dice the onion and unpeeled apple. Melt the lard, and simmer the apple, onion and thyme in it for a half hour. Cool. For the sandwich, spread a slice of liver pate on the buttered bread and then spread flavoured lard on top of that. Layer on the aspic and salt beef. Garnish with onion rings and dill. Serve.