1. **Roast the Butternut Squash:** Preheat oven to 425°F (220°C). Cut the butternut squash in half and remove the seeds. Place the squash on a sheet pan and drizzle with olive oil, 2 tsp salt, garlic powder, and paprika. Place 6 to 8 fresh sage leaves on the pan with the squash. Flip the squash over and rub until the skin is also coated with oil. Bake for 45 minutes, or until soft.
2. **Prepare the Béchamel Sauce:** In a saucepan, melt 6 tbsp butter over medium heat with 8 whole fresh sage leaves. Once the butter is melted and begins to brown, whisk in 5 tbsp AP flour until a paste (roux) forms. Gradually add 2 cups milk, 1 cup at a time, whisking continuously until no lumps remain and the sauce thickens. Stir in 2 cups heavy cream until combined and you have a beautiful, thick, and creamy sauce. Add the remaining 2 tsp salt, 1 tsp pepper, 2 tbsp minced fresh sage, and 3 tsp nutmeg. Stir to combine. (You may remove the whole sage leaves if preferred).
3. **Assemble the Lasagna:** Preheat oven to 375°F (190°C). In a large baking dish, ladle a layer of béchamel sauce and spread it evenly to coat the bottom. Add a layer of lasagna pasta sheets. Then, layer the ingredients as follows:
* Layer of roasted squash, ricotta cheese, and diced pancetta.
* Layer of pasta sheets.
* Layer of béchamel sauce and sliced mozzarella.
* Layer of pasta sheets.
* Layer of roasted squash and ricotta cheese.
* Layer of béchamel sauce and a layer of prosciutto.
* Layer of pasta sheets.
* Layer of roasted squash and ricotta cheese with thinly sliced fresh basil leaves.
Continue layering until you are almost out of ingredients. After the final layer of pasta, cover with béchamel, then sprinkle with dollops of squash and prosciutto, the shredded mozzarella, and a bit more fresh basil.
4. **Bake the Lasagna:** Bake for 45 minutes, or until the top is golden brown and bubbly.
5. **Rest and Serve:** Let the lasagna sit for 10 minutes to set before slicing and serving. Garnish with fresh sage if desired.
