Put the oil and butter into a sauté pan on medium heat. Wait until the butter has melted into the oil, then put the pancetta into the pan. Let the pancetta cook for 5-7 minutes, until crisp and the fat is swimming throughout the pan.
Add the onion and stir until translucent, about 2-3 minutes.
Add the carrot and celery and continue to stir or 3-4 minutes, until slightly softened and the fat is thoroughly coating the vegetables.
Add the ground beef along with a generous pinch of salt and some fresh ground pepper. Break up the ground beef in the pan with a fork or wooden spoon, until it's separated into small chunks. Let the ground beef continue to cook for 5-6 minutes, until it appears gray or brown in color.
Add the milk and drop the heat to medium low. Let the milk continue to bubble until it cooks off and there is little to no milk liquid left.
Add a pinch of nutmeg and stir into the mixture.
Keep the heat at medium low, and add the white wine. Let the white wine bubble until cooked down halfway (should take 5 minutes.)
Add the tomatoes, sun dried tomato paste (or regular tomato paste, if using) and 2 tsp of balsamic vinegar and stir into the mixture. Add another pinch of salt and some fresh cracked black pepper. Continue to stir the tomato mixture until the balsamic vinegar fully combined. Add a bay leaf and stir it so it's fully coated in the sauce.
Lower the heat to a simmer and let the sauce simmer uncovered for 3-5 hours. The more the merrier, but I understand wanting to eat it quickly!! Continue to add splashes (1/4-1/2 cup) of your salted water to the sauce if it looks like it's reducing to a paste. This ensures that it doesn't dry up and that the ingredients keep swimming and simmering to develop flavor.
Check on the sauce after 45 minutes and pulse your immersion blender on low over the tomatoes to open them up and release their juices. Remove the bay leaf, then, run the immersion blender through the sauce 3-4 times, to encourage all of the ingredients to come together and swim in the saucy deliciousness. Put the bay leaf back into the sauce. If you don't have an immersion blender, squash the tomatoes with a fork to break them up. I prefer the blender because it helps the sauce develop the utmost creaminess.
After 3 hours, remove the bay leaf again and run the immersion blender through the sauce on low, another 3-4 times. The goal isn't to blend the sauce because we want our ingredients to maintain their shape, however it helps break them apart and release flavor after soaking in our sauce for so long. You'll see the sauce begin to get even more creamy.
30 minutes before serving, add another teaspoon of balsamic vinegar and stir until combined. Add another splash of water (or skip this if your sauce isn't drying up) and continue to let the sauce simmer. Taste right before serving, and adjust any other seasonings accordingly.
Toss cooked pasta in the sauce and plate. Top generously with freshly grated Parmesan. I also love to top mine with fresh parsley for a pop of bright flavor, but it's completely not necessary and more of a preference.