This hearty lasagna will please your meat lovers, and is more delicious warmed up on Christmas Day evening, when no one wants to do any more cooking. I make my Bolognese sauce December 22nd, and the bechamel December 23rd. Here's what you'll need for everything.
On December 22nd, coarsely chop onion, carrot and celery.
Heat olive oil in large heavy pot over medium heat until it starts to shimmer then add ground beef, ground pork, pancetta and vegetables. Cook, breaking up ground meat with a spoon, until moisture is evaporated and meat is well browned, about 30 minutes, and season with kosher salt and pepper.
Add wine to pot and bring to a boil, scraping browned bits from bottom. Slowly add milk, bring to boil, reduce heat to simmer until moisture is again almost completely evaporated, about 10 minutes. Add tomatoes and 2 cups of broth, bring to boil, reduce heat and simmer, adding water by the 1/2-cupfuls if sauce begins to look dry, and until flavors meld and sauce thickens, which will take nearly 3 hours.
Let sauce come to room temperature, cover and chill in the refrigerator at least 12 hours, and up to 2 days. As it sits, the sauce will become richer with flavor.
On December 23rd, warm milk.
Heat butter in medium saucepan over medium heat until foaming. Add flour, whisking constantly, and cook about 1 minute. Whisk in warm milk, 1/2-cupful at a time. Bring sauce to a boil, reduce heat to simmer, whisking often, and until the consistency of cream, about 10 minutes. Add nutmeg and season with kosher salt. Remove from heat, transfer to a medium bowl, press plastic wrap directly onto surface, let cool to almost room temperature and then chill in refrigerator until ready for use.
On December 24th, preheat oven to 350 degrees and coat 13-by-9 glass baking dish with butter.
Spread 1/4 cup bechamel in the prepared baking dish. Top with a later of 4 noodles, slightly overlapping, spread over a scant 3/4 cup Bolognese sauce, then 1/2 cup bechamel and top with 1/4 cup Parmesan. Repeat layering, starting with noodles and ending with Parmesan, until ingredients are gone. Place baking dish on a rimmed baking sheet because it will bubble over, and bake for 55 minutes, or until top is brown and entire lasagna is bubbling. Let sit at least 15 minutes before serving.
Lasagna can be assembled 12 hours ahead. If you choose to do this, cover with foil and chill in refrigerator. Bring out of refrigerator 2 hours before baking to allow lasagna to come to room temperature. Bake at 350 degrees, covered with foil, until the last 20 minutes, then finish cooking uncovered. Let sit for at least 15 minutes before serving.