Chop the dry sausage in very small pieces. Mix it with the ground beef and a little bit of egg yolk and bread crumbs, such that it becomes a sturdy mass.

Divide it in two burgers and add salt and pepper to taste. Cook the meat for a few minutes on both side. If you would like to you can melt some (Gouda) cheese on them.

Chop the onions and (rucola) lettuce and cut the tomato in slices. Cut the buns in half, smear a teaspoon of mustard on both buns, add the burger, and top of with the vegetables.

Enjoy!