In a Dutch Oven, heat the olive oil and the butter, over medium high heat.
Add the onion and sauté until translucent. Then, add the celery and carrot, cooking for until the begin to caramelize, 5-8 minutes. Add garlic and sauté for another couple of minutes, until fragrant. Season with salt and pepper and, using a slotted spoon, remove the soffritto to a plate and reserve.
Add the ground pancetta and cook until golden brown, about 5 minutes. Remove and reserve.
Working in batches, add the ground beef and ground pork. Season with salt and pepper and cook, breaking lumps with a wooden spoon but resisting the urge to stir too often, until browned, about 10 - 15 minutes. We want the meat to caramelize and the brown bits to stick to the bottom of the pot, as that's where all the flavor is!
Return the reserved soffritto and pancetta back to the pot.
Add the white wine and let it simmer, scraping all the bits from the bottom of the pot, until bubbled away completely.
Add the crushed tomatoes, milk and the grated nutmeg. Season with salt and pepper. When the sauce begins to bubble, lower the heat, cover and simmer for 3 hours, stirring occasionally. If the sauce dries out too much, add a splash of water or milk as needed. Some of the fat will separate and float to the top, making it easier to skim it off with a spoon. Discard.
Stir in heavy cream, parmesan cheese and parsley. Stir vigorously to emulsify. Taste for seasoning and adjust salt and pepper, if necessary. Reserve