Preheat oven to 400º F. Line a baking sheet with parchment paper.
In a large bowl, combine the beef, pork, bacon fat, prosciutto, bread crumbs, parsley, 1 tablespoon salt, oregano, fennel seeds, and chile flakes. Mix gently with your hands until the ingredients are evenly distributed.
In a medium bowl, combine ricotta, eggs, and milk. Whisk until ricotta curds are broken down and mixture is blended.
Add the ricotta mixture to the meat mixture and gently mix with your hands until just incorporated. Form into 1-1/2 inch size balls, weighing about 2 oz. each. Place the balls on the lined baking sheet. You will have about 30 meatballs.
Bake, rotating the baking sheet halfway through, for about 15-20 minutes, or until meatballs are browned and fully cooked.
Remove the meatballs from the oven and lower the temperature to 300º F.In a shallow stoneware baker, place the meatballs and cover with the tomato sauce. Cover tightly with aluminum foil and braise for about 1 hour.
Serve with grated parmesan cheese and a drizzle of extra virgn olive oil.