Cut the prosciutto and pancetta into small pieces and remove the casing from the sausages. Using a meat grinder, grind together the prosciutto, pancetta, and sausages. Place the ground meat in a crockery or glass bowl, add the butter and eggs, and mix very well with a wooden spoon until the butter is completely incorporated. Add the bread crumbs and Parmesan, and season with salt and pepper. Cover the bowl and refrigerate for at least 1 hour before using.
When ready, bring the broth to a boil in a large pot over medium heat. Meanwhile, place a large skillet with the butter over low heat. When the broth reaches a boil, start shaping the meat mixture into tiny meat balls; a heaping tablespoon of mixture will be enough to prepare several. Make sure the meat balls are solid with no holes inside. Drop the balls into the boiling broth a few at a time, and as they rise to the top, tansfer them with a slotted spoon to the skillet containing the butter. When all the meat balls are cooked and in the skillet, add the mascarpone and heavy cream. Mix very well and simmer for 1 or 2 minutes, or until the mascarpone is completely dissolved. Season with salt, pepper, and nutmeg. Mix very well, then transfer to a warmed serving platter. Serve immediately, with some Parmesan on the side.