Preheat the oven to 450° F.
On a sheet pan, add the ground beef and ground pork and spread it out into a thin, even layer. This will help it bake in the oven quickly and evenly.
Bake for 15 minutes.
Allow the meat to rest and soak up all of the juices released.
Once the meat is fully cooled, use your hands and begin breaking up the meat into tiny bits. Be sure to get all of the fat released onto the pan incorporated into the meat. This adds a lot of flavor to the sauce.
While the meat is cooking, set your stove to medium heat and heat the stock pot.
Add 3 Tbsp. of olive oil and 4 oz. of pancetta to the pan and sauté until golden brown
Cut the sweet, celery stalks, carrots, cloves of garlic, and the fennel bulb.
Place the veggies into the food processor and pulse until all the veggies are broken down into small pieces.
Add the veggies into the stock pot with the browned pancetta. Keep all of the fat that has been released from the pancetta in the pan. This will add a lot of additional flavor.
Once the sofrito has cooked down (about 7-8 minutes), add the tomato paste. Cook down for about 1 minute. Stirring continually to avoid burning.
Add the white wine to deglaze the bottom of the pan. Stir to release the bits off the bottom of the pan. Cook down until the wine is about half as much as when you poured it in.
Add canned tomato.
Bring to a simmer, then add whole milk, ground meat, chicken bone broth, and a couple pinches of salt to the pot.
Bake with the lid partially on in the oven at 300° F for 1 hour.
After one hour take the lid off of the stock pot and turn up the oven temperature to 325° F and cook for an additional 45 minutes.
Remove from the oven and skim some of the extra fat off the top if there is an exorbitant amount. Do not remove it all though. The fat adds a lot of richness to the sauce so you want to keep some of it in there and mix it into the sauce.
Add 1 bunch of parsley, 2 Tbsp. of balsamic vinegar, and the remaining one teaspoon of salt.
Scoop the sauce onto your spaghetti, or noodle of choice and top with parmesan cheese.