In a large Dutch oven or heavy bottomed pot, combine olive oil and 3 tablespoons butter over medium heat. 

While the butter is melting, pulse onion, carrot and celery in a food processor until very finely puréed. 

Add puréed veggies and (optional) pancetta to the pot and cook until caramelized, stirring often and gently scraping the bottom to prevent burning where caramelized veggies are sticking, about 10-15 minutes. 

Add ground beef, ground pork, garlic and 1 teaspoon salt and 1 teaspoon pepper. 

Cook until the meat has lost its pink color and is slightly caramelized, stirring often to break it up as much as possible, about 10 minutes. 

Raise heat to medium high. Add milk and stir well. Allow to cook until milk is mostly evaporated. 

Add wine and cook until wine is mostly reduced. 

Add tomatoes and break up with your spoon (they’ll break down as they cook so don’t worry too much about this). Turn heat to low and allow to gently cook for 6-8 hours, stirring periodically. The sauce is done when there’s virtually no liquid left.

Cook pasta according to package directions and add to the sauce. Add in remaining butter and Parmesan cheese and toss together. 

Serve with additional cheese and fresh basil. (Sauce improves if you allow it to sit overnight in the fridge and soak into the pasta).