This recipe is a family tradition. It has been handed down from generation to generation but never written down. There are things I'd like to explain before starting: some of the meats I use are interchangeable. The whole idea of a meat gravy is the different combination of meats, not the exact meats themselves. The two basic meats are pork and beef; some like to add veal, but I don't. Many in my family add their own third meat: some use poultry, mine is lamb. Some in our family only use beef and pork but I find it less tasty. Serve the sauce over your favorite pasta with grated cheese; I recommend Locatelli® Pecorino Romano. I also add meatballs and braciole to the sauce; see links below for those recipes.
The amount of servings is an approximation. Of course you don't have to make this in such a large amount. I make such a large quantity so that I can put it into smaller containers and freeze it. If the tomatoes you use contain puree, you should reduce the amount of tomato paste by half.
You can use pork knuckles for the pork spareribs, and beef short ribs instead of the oxtails. Use all sweet Italian sausage instead of half sweet, half spicy, if you prefer.
I prepare meatball mixture first and put the mixture in the refrigerator until it's time to roll and fry them, to allow the flavors to marry. Don't fry them until the sauce is cooking. When finished frying, deglaze the frying pan lightly with some sauce and return the sauce to the pot. See my recipe for Bon Appetit's Meatballs.
I make my Braciole with beef and pork wrapped around Genoa salami. Add them about two hours into the cooking time (see Step 6) so that they'll have about 2 to 4 hours of simmering time. Before serving, slice the braciole and remove the kitchen twine.