All ingredients ready? Let's begin!
In a large saucepan over medium heat, cook the pancetta until it starts to brown, about 5 minutes. Using a wooden spoon, stir the pancetta a few times.
Add the olive oil, onion, carrot, and celery to the pot. Stir well to combine and continue to cook for another 5 minutes.
Add the ground beef to the vegetables and pancetta and cook until it browns, approximately 5 minutes, stirring a few times.
Add the white wine and deglaze the pan, scraping up any brown bits. Allow the wine to cook off completely. Stir in the tomato passata or crushed tomatoes and the beef stock. As soon as the liquid bubbles, turn the heat to a low simmer, cover the pot, and cook the Bolognese sauce for 2 hours. At about 1-1/2 hours, stir in the milk. You want a fairly thick and chunky sauce. Add a little extra stock if needed. Season the sauce with salt and pepper to taste.
While the Bolognese sauce is almost finished simmering, prepare the bechamel sauce. In another saucepan over low heat, melt the butter. Whisk the flour into the butter and cook until you have a golden-colored roux. This will only take about 30 seconds to 1 minute, whisking constantly.
Slowly stream the milk into the roux, whisking the entire time so lumps don’t form. Keep whisking until you have a thick yet pourable bechamel sauce. This could take about 10 minutes or more until the bechamel coats the back of a wooden spoon. Season with salt and nutmeg and set aside.
Preheat your oven to 380°F. Before assembling the lasagna, you will need to blanch the fresh pasta in boiling water and then drain it. If you are using the dried, no-boil pasta sheets, there is no need to blanch them.
In a 9 x 13-inch glass or ceramic baking dish, spread out 2 tablespoons of the bechamel. Place the lasagna noodles in a single layer over the bechamel. You can cut the sheets. Spread a layer of 2 tablespoons of Bolognese sauce over the pasta. Spoon another 2 tablespoons of bechamel over the sauce. Sprinkle this with 2 tablespoons of parmesan cheese.
Continue step 9 until you have at least 5 layers and up to 7 to fill the baking dish. Finish the top layer of sauce and bechamel with a good amount of parmesan so it gets browned and crisp. Bake for 30 minutes until bubbling.
Remove the lasagna from the oven and allow it to cool for 10 minutes before slicing into it. Serve while warm.