In a large pot, heat olive oil over medium heat. Add the chopped onion, carrots, celery, and garlic. Sauté until the vegetables are softened.
Add the ground beef and pork to the pot. Cook until browned and crumbled, ensuring there are no large chunks.
Pour in the red wine and let it simmer until reduced by half.
Stir in the crushed tomatoes, tomato paste, dried oregano, dried basil, salt, and pepper.
Add the milk and broth, then bring the sauce to a simmer. Reduce the heat to low, cover the pot, and let it simmer for at least 2 hours, stirring occasionally.
Meanwhile, cook the spaghetti according to package instructions. Drain and set aside.
Adjust the seasoning of the Bolognese sauce and serve it over the cooked spaghetti.
Garnish with grated Parmesan cheese and fresh parsley.