Mix together first 4 ingredients. In 9 x 13 inch cake pan, layer rye bread with mustard on it, 1/2 cup Swiss cheese, corned beef, drained sauerkraut, 1/2 cup Swiss cheese, pour egg and milk mixture over this. Refrigerate for a minimum of 4 hours, preferably overnight. Bake at 300 degrees for 1 hour.
Dan prefers to add Russian dressing or Thousand Island dressing on this when eating it.