Making the rolls:
Cut onions into strips and sauté in a little butter. Add salt and pepper and set aside to cool. Remove tendons from meat and cut into slices. Beat slices with a meat pounder, brush with mustard, sprinkle with marjoram and top with sautéed onions. Roll up the meat slices into rolls. Butter the aluminum foil, wrap the rolls in it and sauté them in the olive oil in a frying pan, about 2 minutes on each side. Immerse the rolls (still wrapped in aluminum foil) in hot water at 70° C and cook for 8 hours. Or, bake in the oven.
Making the sauce:
Sautée the veal bones in a little olive oil in a frying pan. Add the vegetables. Add the tomato purée and continue cooking slowly. Sprinkle with flour and brown. Add Port and red wine and continue cooking until most of the liquid has evaporated. Add the veal broth and bring to a boil, stirring constantly. Boil the sauce for about 3 hours over a low flame. Take the sauce off the fire and add spices and herbs; do not cook any more, but set aside for about ½ an hour, then add salt and pepper. Strain the sauce.
Remove the rolls from the aluminium foil and heat them gently in the sauce (without cooking them) before serving. Serve with fresh vegetables in season, mashed potatoes or Canederli Enjoy!