Sauté flour in butter, add beef broth, bring to a boil while stirring and make a few minutes at low temperature. Add cheese, let it melt and season with salt and pepper. Stir the egg yolk whisked with whipped cream into the soup, do not make more. Dice the toast and toast it in butter. Pour soup into plates, sprinkle with parsley and bread cubes.
(Biberacher Leispeisen, Cath. parish council St. Martin, Biberach)