Heat 1 tablespoon of olive oil and 2 tablespoons of butter in a large Dutch oven over medium heat. Crisp 6 oz of diced pancetta for about 5 minutes until golden. Add 1 lb of ground sirloin and 1 lb of ground Italian sausage, cooking until browned. Stir in a finely minced mixture of 1 cup yellow onion, 1 cup carrots, and 1 cup celery, cooking for another 5 minutes until softened. Incorporate 4 cloves of minced garlic and allow to cook until fragrant. Stir in 6 oz of tomato paste, then pour in 1.5 cups of medium-bodied red wine and 1 cup of whole milk. Finally, add a 28 oz can of crushed tomatoes, 2 bay leaves, and a piece of Parmesan rind. Allow the sauce to simmer gently on low heat for 2.5 to 3 hours, stirring occasionally until deeply flavorful.

Bring a large pot of salted water to a boil. Carefully add 20 sheets of egg lasagna noodles, cooking them for about 4 minutes until al dente. Using a slotted spoon, transfer the noodles to a parchment-lined baking sheet, drizzling them lightly with olive oil to prevent sticking. Allow the noodles to cool while preparing the béchamel sauce.

In a medium saucepan over medium-low heat, melt 5 tablespoons of unsalted butter. Whisk in 1/4 cup of all-purpose flour, cooking for 2 minutes until lightly golden. Gradually add 4 cups of warmed whole milk, whisking constantly to achieve a smooth, thickened consistency—about 8 minutes. Once thick, stir in 2.5 cups of freshly grated Parmesan, 1/8 teaspoon of freshly grated nutmeg, and season with salt and freshly cracked pepper to taste.

Preheat your oven to 375°F (190°C). Grease a 9x13 inch baking dish with a little olive oil. Spread a thin layer of béchamel sauce on the bottom of the dish, followed by a layer of cooked noodles, then a generous amount of the Bolognese sauce. Repeat the layering process with béchamel, noodles, Bolognese, and 16 oz of diced fresh mozzarella. Continue this until all ingredients are used, finishing with a layer of béchamel and a sprinkle of the remaining Parmesan on top.

Cover the assembled Lasagna Bolognese with aluminum foil and bake in the preheated oven for 1 hour. Afterward, remove the foil and bake uncovered for an additional 15 minutes until the top is golden and bubbly. Once baked, allow the lasagna to rest for at least 20-30 minutes before slicing.