Cook the beef in salted water for about 45 minutes. Remove the bones from the cooked beef. Save the broth. Cut the meat into bite-sized pieces and keep warm in the broth.
Finely chop the herbs and the onion and sauté in a pan with the butter, add 1/8 liter of the broth. Remove the finely chopped meat from the broth and simmer in this herb and onion stock for about 15-20 minutes.
Arrange on a preheated plate.
Mix the sauce with the mustard, vinegar and sugar. Add the finely chopped capers and the finely diced pickles. Serve the sauce with the meat.