Sauté the aromatics — Heat the olive oil in a large pot over medium heat and add the finely diced onion, carrot, and celery. Cook until softened and translucent, about 8 minutes, ensuring they don't pick up too much brown color.

Render the pancetta — Stir in the diced pancetta and cook for another 5 minutes. You want the fat to render out until the edges of the pork start to look golden and slightly crisp.

Brown the meats — Increase the heat slightly and add the ground beef and pork. Break the meat apart with a wooden spoon and cook until it is no longer pink and has developed a nice sizzle, but avoid hard-searing it into dry crumbles.

Deglaze with wine — Pour in the white wine, scraping the bottom of the pot to release any flavorful browned bits. Let it simmer until the liquid has reduced by about half and the sharp scent of alcohol has vanished.

Simmer with liquids — Add the beef stock, the Parmesan rind, the rosemary sprigs, and half of the milk. Season with a bit of salt and pepper, then turn the heat to low and let it gently bubble for at least 45 minutes to develop depth.

Finish the sauce — Stir in the remaining milk and the ground nutmeg. Remove the rosemary sprigs and the Parmesan rind (which should be soft and stretchy now).

Emulsify with pasta — While the sauce finishes, boil your pasta in salted water until just shy of al dente. Reserve 1.5 cups of the starchy water before draining.

The final toss — Add the pasta, reserved water, and grated Parmigiano Reggiano to the meat sauce. Toss vigorously over medium heat for 2 minutes until the sauce turns glossy and coats every strand of pasta perfectly.