Peel the chestnuts and cook them in salted water, then liquidise them in a blender. Keep 6 whole to garnish. Peel the sausages and mix their meat with the chestnuts in a bowl. Add the egg, pepper and grated Parmesan cheese. Be careful not to thicken the mixture too much. Lay the veal belly on a table and spread on top a layer of chestnut mixture. Place the whole chestnuts in a line, then roll the veal up and tie it with a string. Oil the roll, place it in a baking tray and cook in a pre-heated oven for about 90 minutes, turning it every now and then. When cooked, remove it from the oven and let it cool a little. When it is warm, remove the string, slice it and serve it.