Summarize this article in one sentence.
In a large pot, melt the butter completely over medium heat. Add in the flour and whisk until smooth. Gradually add in the milk, continuing to whisk and simmer over medium heat for about 10 minutes. The sauce should be thick, smooth, and creamy when finished. Set aside and allow to cool completely. Season with salt and pepper and cook the meat until it is browned. Drain the excess fat and set aside, allowing to cool completely. Add in the ricotta cheese, salt, and pepper and then mix thoroughly. Cover it with one layer of pasta, overlapping the pasta slightly to make sure the entire dish is covered. Follow with one layer of spinach, and then add another layer of pasta sheets. Cover it with 1 1/2 cups of mozzarella cheese. Arrange another layer of pasta on top, and then spread the remaining bechamel sauce over it. Sprinkle with the remaining mozzarella and Parmesan cheeses. Remove the cover and bake for an additional 15 minutes. Enjoy with a glass of red wine if you are old enough.

Summary:
Preheat the oven to 375 degrees Fahrenheit (190 degrees Celsius). Prepare the Bechamel sauce. Heat extra-virgin olive oil in a sauté pan and then add the ground beef. In a medium-sized bowl, whisk the eggs. Spread an even layer of the Bechamel sauce (about 1/3 of it) into the bottom of a baking dish. Cover with one layer of the ricotta mixture. Add all of the ground beef in an even layer. Spread another 1/3 of the Bechamel sauce over the mozzarella. Cover the lasagna with aluminum foil and bake for about 30 minutes. Allow to cool before serving.