2 medium onions, peeled, finely chopped
4 celery ribs, finely chopped
2 medium carrots, peeled, finely chopped
5 garlic cloves, peeled, minced
1/4 cup extra-virgin olive oil
1/4 pound pancetta or slab bacon, finely chopped
1 pound ground beef
1 pound ground pork
1 (6-ounce) can tomato paste
1 cup whole milk
1 cup dry white wine
1 cup water
1 teaspoon fresh thyme leaves
1 1/4 teaspoons kosher salt
1/2 teaspoon black pepper
In a heavy pot saute' onions, celery, carrot, and garlic in oil, stirring occasionally, until softened, about 5 minutes. Add pancetta, beef and pork and cook over moderately high heat, stirring and breaking up lumps, until no longer pink, about 6 minutes.
Stir in tomato paste, milk, wine, water, and thyme and gently simmer, covered, until sauce is thickened, 1 to 1 1/2 hours. Add salt and pepper and remove from heat.
Sauce may be made 2 days ahead and cooled, uncovered, before chilling, covered. Frozen, it keeps for 1 month.
