Preheat your oven to 400 degrees Fahrenheit. Line a baking sheet with parchment paper for easy cleanup.
Arrange the butternut squash cubes on the baking tray. Drizzle with olive oil, and sprinkle with salt and pepper. Toss the cubes to ensure they are evenly coated with the seasoning. Roast for about 30 minutes, or until tender and slightly caramelized. Remove the tray from the oven and allow the squash to cool.
In the meantime, prepare the béchamel sauce. In a medium pot over medium-high heat, melt the butter. Once melted, add the flour and whisk together for about one minute, creating a roux. Gradually add the milk in three portions while continually whisking to achieve a smooth consistency.
Allow the béchamel sauce to simmer on medium-low heat for about 8 minutes until it thickens. Stir occasionally to prevent lumps. After thickening, remove the sauce from the heat and stir in the freshly grated nutmeg.
When the sauce has cooled slightly, take one-third of it and blend it with the fresh basil leaves in a food processor until smooth. Combine this basil-infused sauce back with the remaining béchamel, creating a lovely green sauce.
Add the Parmesan cheese and two tablespoons of the crushed Amaretti cookies to the béchamel sauce and mix until well incorporated. Season with additional salt and pepper to taste, and set aside.
To prepare the filling, take the roasted butternut squash and puree it in a food processor with the remaining Parmesan cheese and the remaining Amaretti cookies until smooth. This will be the delicious filling for your lasagna.
Now it’s time to assemble the lasagna. Butter the bottom and sides of a 9”x13” baking dish. Ladle ¾ cup of the basil béchamel sauce at the bottom. Layer 2 to 3 sheets of lasagna (depending on the size) on top, ensuring the entire surface is covered.
Spread half of the butternut squash puree over the pasta evenly. Top this layer with a drizzle of béchamel, followed by a sprinkle of parmesan cheese, a handful of mozzarella cheese, and a few tablespoons of Amaretti cookies.
Repeat the layering process two more times, finishing with a final layer of béchamel sauce. Cover the dish with foil and bake in a preheated 375 degrees Fahrenheit oven for about 30 minutes.
After 30 minutes, remove the foil and add the remaining mozzarella cheese on top. Bake uncovered for an additional 10 minutes, or until the cheese is melted and bubbly. Once done, remove from the oven, sprinkle with fresh basil, and allow to cool for 10 minutes before serving.
