Blend the cloves, bay leaf, fennel seeds, red pepper flakes, and peppercorns in a spice mill and finely grind. Set aside.
In a large skillet add the cubed pancetta (or bacon) and brown until rendered and crispy. Remove from pan and place on plate lined with paper towel. Set aside.
In same skillet remove all but 1 tablespoon of fat and save remaining for other use. Add the onions, carrots, celery and salt, stirring as needed until golden in color, about 5-6 minutes. Add the garlic and stir, cooking another 2 minutes.
Add the sauteed vegetables to a slow cooker coated with cooking spray. Stir in the spice mixture, pancetta, ground beef (uncooked), pork sausage meat (uncooked), red wine, tomatoes and tomato paste. Stir to incorporate, breaking up meat and top with lid. Cook for 4 hours on high setting.
At the 4 hour mark, remove lid of slow cooker. Stir in the the milk and cook on high setting for 2 hours or until thickened and reduced. Add the vinegar, stirring to incorporate, and adjust seasoning with salt if needed.
Cook pasta in a large pot of boiling, heavily salted water, stirring occasionally, until al dente (or package directions). Drain, reserving 1 cup pasta cooking liquid.
Toss pasta and butter in a very large skillet set over medium heat. Using ladle add 2 cups of sauce to coat pasta and cook, adding some of the pasta cooking liquid as needed, until sauce is thick and glossy.
Serve topped with a scoop of Burrata cheese (as shown), or shredded Parmesan cheese and fresh basil leaves.
Save balance of bolognese sauce for other use or freeze.
Video
Notes
The ground beef and pork sausage meat go in uncooked. No need to brown prior to adding to slow cooker.
This bolognese recipe makes enough for 8 people or more depending on portions. I've included directions for pasta, but it's only for 4 servings. Save remaining sauce in refrigerator covered, or freeze for later use. Nutrition information is for bolognese sauce only.