German Liver Dumpling Soup

10 cups beef stock
1 small onion, finely diced or 1/2 large onion, finely diced
350 grams sandwhich bread
1 egg
1 egg yolk
300 grams liver, ground
salt, pepper, nutmeg to taste
1/2 tablespoon dried marjoram
1/4 cup fresh finely chopped parsley
zest from one small lemon
1 bay leaf
1 tablespoon dijon mustard
* may need to adjust the consistency of the dumpling using egg yolk or beef stock if too dry or more bread crumbs if too wet*
** fresh parsley for garnish when serving**
*** best made the day before***