Prepare the Soffritto Base: In a large sauté pan, melt the butter over medium heat. Add the diced pancetta, onion, celery, and carrot. Cook gently, stirring often, until the onion softens and becomes a pale golden color—this slow sauté builds a fragrant vegetable base essential for the sauce.
Brown the Meat Mixture: Increase heat to medium-high and add the ground beef, pork, and Italian sausage to the soffritto. Cook, stirring and breaking up the meat, until browned evenly. Sprinkle in the ground clove, cinnamon, and black pepper. This step develops complex layers of flavor and richness.
Incorporate Tomatoes and Simmer: Stir in the peeled, chopped tomatoes, breaking up any large pieces if using canned. Bring the mixture to a gentle simmer, then lower the heat to medium and cook for about 15 minutes, allowing the tomato flavors to meld with the meat.
Add Milk and Slow Cook: Pour in the whole milk and season with sea salt. Reduce heat to low and let the sauce simmer uncovered for 2.5 hours, stirring every 20 minutes to prevent sticking. If the sauce reduces too much and begins to stick, add 1/4 cup water and scrape the bottom to lift browned bits. This slow simmer yields a rich, thick sauce with deep flavor.
Make the Béchamel Roux: Warm the milk in a saucepan until nearly boiling, then set aside. In a separate heavy-bottomed pan, melt butter over low heat. Stir in the flour, whisking continuously for about 1 minute to create a smooth paste without browning. This roux is the base for the creamy béchamel.
Combine Milk with Roux: Gradually pour half the hot milk into the roux while whisking constantly to avoid lumps. Once smooth, return the mixture to low heat and slowly add the remaining milk, whisking until the sauce thickens and comes to a gentle boil. Season lightly with sea salt. If lumps form, vigorously whisk them out.
Prepare the Pasta Sheets: Cook the lasagna noodles in boiling salted water for about 8 minutes or until just tender (al dente). Drain and rinse under cold water to stop cooking. Lay noodles flat on clean kitchen towels without overlapping to keep them from sticking.
Assemble the Lasagna: Preheat the oven to 375°F (190°C). Lightly grease a 13x9-inch non-reactive baking dish (glass or stainless steel preferred). Start by layering noodles on the bottom. Spread one-third of the Bolognese sauce evenly over the noodles, followed by one-third of the béchamel sauce, then sprinkle with Parmesan. Repeat this layering two more times. Finish with a top layer of noodles and a final Parmesan sprinkle.
Bake and Rest: Cover the assembled lasagna with foil and bake in the oven for 20–30 minutes, until the top is lightly golden and bubbly. Remove from oven and let rest for 5 to 10 minutes before slicing to allow the layers to set properly.