Heat olive oil and butter in a large Dutch oven or heavy-bottomed pot over medium heat. Add the onion, carrot, and celery and cook, stirring occasionally, for 10-12 minutes until softened and lightly golden. Add the garlic and cook for another 1 minute until fragrant.

Add the ground beef and ground pork to the pot. Break up the meat with a wooden spoon and cook over medium-high heat, stirring frequently, until fully browned and any liquid has evaporated, about 10 minutes.

Pour in the white wine and stir, scraping up any browned bits from the bottom of the pot. Let the wine cook off completely, about 5 minutes.

Pour in the whole milk and stir to combine. Let the milk absorb into the meat over medium heat, about 5 minutes.

Stir in the crushed tomatoes, tomato paste, salt, pepper, nutmeg, and bay leaves. Bring to a gentle boil, then reduce the heat to the lowest setting. Partially cover and simmer, stirring occasionally, for at least 1.5 to 2 hours until the sauce is thick, glossy, and deeply reduced. Remove bay leaves and adjust seasoning.

For best results, let the ragù cool and refrigerate overnight — the flavor deepens significantly.

In a medium saucepan, melt the butter over medium heat. Add the flour all at once and whisk constantly for 1-2 minutes to cook out the raw flour taste (it should smell faintly nutty but not brown).

Slowly pour in the warmed milk a little at a time, whisking constantly to prevent lumps. Continue adding milk and whisking until all the milk is incorporated and the sauce is smooth.

Continue cooking over medium heat, whisking frequently, until the béchamel thickens enough to coat the back of a spoon, about 8-10 minutes. Season with salt, white pepper, and nutmeg. Remove from heat and stir in the Parmigiano-Reggiano. Cover with plastic wrap pressed directly against the surface to prevent a skin from forming.

If using dried lasagna noodles, bring a large pot of heavily salted water to a boil. Cook the noodles 2 minutes less than the package directions (al dente). Drain and lay flat on a lightly oiled baking sheet to prevent sticking. If using fresh pasta sheets, no pre-cooking is needed.

Preheat your oven to 375°F (190°C). Lightly butter the bottom and sides of a 9x13 inch baking dish.

Spread a thin layer of béchamel across the bottom of the dish. Lay down a layer of pasta sheets, slightly overlapping to cover the bottom completely.

Spread an even layer of Bolognese ragù over the pasta, followed by a generous layer of béchamel. Sprinkle with a handful of Parmigiano-Reggiano.

Repeat the layers — pasta, ragù, béchamel, Parmigiano — until you have 4 to 5 layers, ending with a final layer of pasta topped with the remaining béchamel. Sprinkle generously with the remaining Parmigiano-Reggiano and dot the top with small pieces of butter.

Cover tightly with aluminum foil (tent it slightly so it doesn't stick to the cheese) and bake for 35 minutes. Remove the foil and bake for an additional 20-25 minutes until the top is deeply golden and the edges are bubbling vigorously.

For an extra-crispy Parmigiano crust, broil on high for 2-3 minutes at the very end — watch carefully. Remove from the oven and let rest for at least 15-20 minutes before slicing and serving.

Use a sharp spatula to cut and lift clean slices. Serve with a simple green salad and a glass of Sangiovese or Chianti. Finish with an extra grating of Parmigiano-Reggiano at the table.