Step 1

Combine the beef and pork in a large bowl. "Pull" the ground meat apart with two forks as if you were shredding pulled pork, breaking up the clumps and incorporating the meat without compacting it. Continue to pull the meat apart until thoroughly mixed and no clumps remain.

Step 2

Heat the oil in a Dutch oven or large heavy pot over medium-high heat. Cook the pancetta, stirring occasionally, until the fat has rendered and is golden brown on all sides, 4 to 6 minutes. Transfer the pancetta with a slotted spoon to a large bowl, leaving the fat in the pot.

Step 3

Spread half of the ground meat in an even layer in the pot and cook undisturbed until lightly golden brown, 1 to 2 minutes. Toss and continue to cook, breaking up any clumps with the back of a spoon and scraping up any browned bits from the pot, until the meat is lightly browned on both sides, 1 to 2 minutes more. Transfer the browned meat with a slotted spoon to the bowl with the pancetta, leaving the fat in the pot. Repeat with the remaining ground meat.

Step 4

Reduce the heat to medium. Add the garlic, celery, carrots, onions, bay leaf, nutmeg, 2 teaspoons salt and 1/4 teaspoon pepper and cook, stirring occasionally, until the vegetables are tender but not browned, 8 to 10 minutes. Add the tomato paste and cook, stirring constantly, until very fragrant and brick red, about 2 minutes. Stir in the wine, bring to a boil and cook until it reduces and thickens and no smell of alcohol remains, 6 to 8 minutes. Stir in the stock, milk and browned meat.

Step 5

Bring to a boil, then reduce the heat to low. Add the Parmesan rind and simmer, stirring occasionally, until most of the liquid has evaporated away and the mixture resembles sloppy joes, 2 to 2 1/2 hours. There shouldn't be any rapid bubbles while cooking. Instead, the sauce should release occasional small bubbles. If you have a small burner you should use it; the larger burners even at their lowest setting might cook the sauce too quickly. If the sauce reduces too quickly, add 1/2 cup of stock or water and continue cooking; repeat if necessary. The sauce needs the full 2 to 2 1/2 hour cook time to develop the flavors.

Step 6

Discard the bay leaf and Parmesan rind. Use the back of a spoon to break up any remaining clumps of meat for an even-textured sauce. Season with salt and keep warm.

Step 7

Bring a large pot of salted water to a boil over high heat. Cook the pasta. If using fresh pasta, cook about 3 minutes. If using dry, cook until very al dente, about 2 minutes less than the package directions.

Step 8

Reserve 1 cup of the pasta cooking liquid, then drain the pasta and transfer to the sauce. Increase the heat to medium, bring the sauce to a simmer and cook, tossing the pasta constantly, until the pasta is al dente and the sauce is slightly thickened, adding pasta cooking liquid if necessary, about 2 minutes.

Step 9

Transfer the pasta to a platter and top with grated Parmesan.