1. Soak the white bread in the milk for about 10 minutes. Meanwhile, melt the 2 tablespoons of butter in a small skillet, and over moderate heat cook the chopped onions in the butter for 7 or 8 minutes, stirring frequently, until they are transparent but not brown.
2. Transfer the onions to a large mixing bowl, and add the ground pork, veal, pork fat, the chopped sweetbread, grated Parmesan cheese, chopped spinach, marjoram, thyme, salt and the egg.
3. Knead all of the ingredients together with your hands or beat them with a wooden spoon until they are well mixed and fluffy. Squeeze the soaked bread dry and mix it in with the other ingredients. Then gently fold in the shelled pistachio nuts and peas.
4. Spread about half of this stuffing evenly in the veal pocket and on top of the stuffing arrange the hard-cooked eggs lengthwise in a row. Spoon in the rest of the stuffing, covering the eggs completely. Sew up the opening of the pocket with strong kitchen thread.
5. Place the veal bones and trimmings (if available), onion halves, garlic cloves, carrot, bay leaf and parsley in a large soup pot or kettle and lay the stuffed veal on top of them. Add enough stock or water to cover the meat completely, and grind in a little black pepper.
6. Bring to a boil, reduce the heat, cover the pot and simmer as gently as possible for 1¼ hours, or until the veal is tender when pierced with the tip of a sharp knife.
7. Transfer the stuffed veal to a large, heavy, shallow baking dish and let it cool to room temperature. Then place the dish in the refrigerator until the meat is thoroughly chilled. Serve cold, cut into ¼-inch slices.
