How to Make It
In a skillet, melt the butter in the oil. Add the ground meat, onion and garlic and season with salt and pepper. Cook over moderate heat, stirring to break up lumps, until the meat is cooked and the onion is tender, 10 minutes. Add the wine and cook over moderately high heat until evaporated, 4 minutes.
Scrape the mixture into a food processor and pulse until the meat is finely chopped. Scrape the ravioli filling into a bowl and let cool. Stir in the Parmigiano, mortadella, prosciutto and nutmeg and season with salt and pepper. Stir in the beaten egg.