Combine pancetta, onion, celery, and carrot in sauté pan with butter and cook over medium heat until onion turns pale gold, about 10 minutes.
Add the beef, pork, and sausage to the soffritto, and cook until browned, about 5 minutes.
Sprinkle with the clove, cinnamon, and pepper.
Add the tomatoes and simmer: Stir in tomatoes, increase the heat to bring to a simmer and then reduce the heat back to medium. Cook over medium heat for 15 minutes. If you are using whole canned tomatoes, break them up as you add them to the sauce.
Add milk and season with sea salt. Then turn down the heat to low, partially cover, and simmer for 2 and 1/2 hours. Stir at least every 20 minutes.
Whenever the sauce gets too dry and starts sticking to the pan, just add 1/4 cup of water and scrape up any browned bits from the bottom of the pan.
Serve: Bolognese is traditionally served with fresh tagliatelle pasta, but you can also serve it with fettucine, pappardelle, penne, or other pasta. Sauce freezes well for future use.