Heat the olive oil in a large, heavy-bottomed pot or Dutch oven over medium heat. Add the onion, carrots, and celery, and cook for 8-10 minutes, stirring occasionally, until the vegetables are softened and slightly golden.
Add the minded garlic and cook for an additional 1-2 minutes, until fragrant.
Next, add the ground beef and pork to the pot, breaking the meat apart with a wooden spoon. Season with salt and pepper. Cook for 10-12 minutes, stirring occasionally, until the meat is browned and cooked through.
Pour in the milk and allow it to simmer for 5 minutes, stirring occasionally, until it has mostly evaporated.
Add the red wine to the pot and let it simmer for another 5 minutes, allowing the alcohol to cook off and the flavors to meld.
Stir in the crushed tomatoes, diced tomatoes, tomato paste, bay leaves and oregano. Bring the sauce to a boil, then lower the heat to a gentle simmer. Cover the pot with a lid, leaving a small gap for steam to escape.
Simmer the sauce on low heat for 2-3 hours, stirring occasionally, until it has thickened and the flavors have deepened. If the sauce becomes too thick, add a bit of water or chicken broth to thin it out.
Once the cooking time has elapsed, remove the bay leaf and stir in the grated Parmesan cheese. Taste the sauce and adjust the seasoning with additional salt and pepper, if needed.
Serve the Bolognese sauce over cooked pasta, such as spaghetti or pappardelle, and garnish with chopped fresh parsley.