Heat the olive oil (or fat from stock) in a casserole. Add the onion and sauté over medium heat until the onion is translucent.
Add the pork, chicken, and beef, and sauté over medium high heat until the meat has lost its raw color on all sides. Add the rosemary.
Deglaze with the Bardolino.
Scrape with a wooden spatula to include the browned bits into the sauce.Add the clove, nutmeg, and season with salt and pepper.Cover and reduce the heat to low.Allow to simmer over low heat until the meat is tender, about 1 hour. Add a bit of meat stock if it becomes too dry.At the end of the cooking time (it is not very important that the meat is tender, as it will be ground anyway), remove the clove.Transfer the contents of the casserole to the food processor, including all the juices. Allow to cool somewhat (so the egg yolk won’t be cooked when you add it).Add the prosciutto, bread, and egg yolk as well as the cheese.Process with the ‘pulse’ until the mixture is homogeneous, but not pureed. It is nice to have some texture. Taste and adjust the seasoning with salt and freshly ground black pepper. Remember that the filling of tortellini and ravioli should always be slightly over-seasoned to avoid that your tortellini will end up tasting bland.Transfer the filling to a bowl, cover with plastic wrap, and refrigerate for an hour to firm up.Make pasta dough and roll it out as thinly as you can. Cut the pasta dough into 5 cm (2 inch) squares, and put a small ball of filling (about 1/2 teaspoon) on each square.Fold each square into a triangle, and seal the edges without trapping any air inside.Fold the tortellini around your finger, then fold it backwards. (That last step is not really needed.)
Transfer them to the butter and sage with a slotted spoon.Toss the tortellini in the butter and sage to coat them on all sides.