In a large saucepan or Dutch oven, heat the butter and olive oil over medium heat.
Add the onion, carrot, celery, and garlic. Sauté until softened and lightly golden.
Increase the heat to medium-high. Add the minced beef, pork, and pancetta (if using) to the pan.
Cook, stirring frequently, until the meat is browned and any liquid has evaporated.
Pour in the white wine and cook until most of the liquid has evaporated, about 2-3 minutes.
Stir in the passata (strained tomatoes) and season with salt and pepper to taste.
Bring the sauce to a gentle simmer, then reduce the heat to low. Cover partially with a lid and let it simmer for at least 2 hours, stirring occasionally. Add water if needed to maintain a saucy consistency.
Pour in the whole milk and stir to combine. Continue simmering for an additional 30 minutes to 1 hour, until the sauce has thickened and the flavors have melded.
Season the ragù with freshly grated nutmeg (if using) and adjust salt and pepper to taste.
Meanwhile, cook the pasta in a large pot of salted boiling water according to package instructions until al dente. Reserve a cup of pasta cooking water.
Drain the cooked pasta and add it to the ragù alla Bolognese. Toss well to coat the pasta evenly with the sauce.
If the sauce seems too thick, add a splash of reserved pasta cooking water to loosen it.
Serve immediately, garnished with freshly grated Parmesan cheese if desired.
