Combine the chopped pancetta, onions, carrots and celery on a cutting board; chop them together into very small pieces. (This mixture is called a battuto, which, when cooked, becomes a soffritto.)
In a heavy 10-inch to 12-inch skillet, over moderate heat, melt 2 tablespoons of the butter.
When the foam subsides, add the battuto; cook, stirring frequently, for about 10 minutes, or until it is lightly browned.
With a rubber spatula, transfer the soffritto to a heavy 3-quart to 4-quart saucepan.
Heat 2 tablespoons of olive oil in the same skillet and lightly brown the ground round steak and pork, over moderate heat, stirring the meat constantly to break up any lumps.
Pour in the wine, increase the heat, and boil briskly, still stirring constantly, until almost all of the liquid in the skillet has cooked away.
Add the meat to the soffritto in the saucepan and stir in the stock and tomato paste.
Bring to a boil, over high heat; reduce the heat and simmer, partially covered, for 45 minutes, stirring occasionally.
Meanwhile, over high heat, melt 2 more tablespoons of butter in the original skillet; when the foam subsides, add the chicken livers; cook for 3 or 4 minutes, or until they are firm and lightly browned.
Remove the livers from the heat and chop them into small dices; set aside and add them to the sauce 10 minutes before it is done.
A few minutes before serving, stir in the cream and let it heat through.
Taste the ragù and season with nutmeg, salt and pepper.
Serve the ragù on pasta or, without the cream, use it in lasagna pasticciate (all a mess or messed up - the idea being that the assembly of this lasagna contains a variety of ingredients and is “all messed up").