Heat the olive oil in a reasonable large pot. Add the onions, celery, carrot, and garlic and cook until soft but not browned. Add the ground meat, sausage, and pancetta, increase the heat, and brown the meat. Add the tomato paste and cook for a minute or so before adding the milk, wine, and thyme. Bring it to a boil and reduce. Simmer for 1½ hours at least. Season to taste.

NOTE: This is based on Mario Batali's Bolognese. Ground pork or veal is particularly nice, but ground beef and even ground turkey are still quite good. Sweet italian sausage will provide a nice fennel flavor, but you could use hot sausage as well.