About 1 lb (400 g) lean beef
(choose a good quality that has not been hung too long).
Freshly grated horseradish
Scrape the meat off the sinews with a short, sharp knife and spread the slices of buttered rye-bread with a half-inch (1 cm) layer of meat.
Make a hollow in the centre, circle it with an onion ring and place a raw egg yolk in each.
Decorate with the horseradish, capers and chopped onion.
Instead of raw beef, you can fry the beef i butter and have a "Pariserbøf".