Cut tops off pumpkins, and set aside. Scrape out seeds, and discard them. Place pumpkins on a baking sheet, and roast them until tender, about 30 minutes. Remove them from oven, scrape out all flesh from 4 pumpkins and transfer flesh to a bowl. Discard shells. Remove most of flesh from remaining 6 pumpkins, and transfer to a bowl, reserving shells for further baking.
Heat a large skillet over medium-high heat, and when it is hot, add 1 tablespoon butter. Add onion, and sauté it for 2 minutes. Add brown sugar, and cook for 2 minutes more, stirring occasionally.
Add pumpkin flesh, and stir it well. Add broth, and bring mixture to a boil. Reduce heat to medium, and cook until pumpkin starts to fall apart, for about 10 to 12 minutes. Add ½ cup almonds, transfer to a blender or food processor and purée. Add remaining 3 tablespoons of butter, salt and pepper. Return mixture to skillet, and reheat it.
Bring a large pot of water to a boil over high heat, add lasagna sheets and cook them until al dente, for 3 to 4 minutes. Remove lasagna from heat, and drain. Place sheets in skillet with pumpkin sauce, and toss. Using tongs, remove sheets, and place them in bottom of shells. Spoon sauce over lasagna, and sprinkle one-quarter of remaining almonds and one-quarter of amaretti, parmesan cheese and mascarpone over top. Repeat until pumpkins are filled, or all ingredients are used up, with a final layer of almonds, amaretti, parmesan cheese and mascarpone.
Bake for 15 to 20 minutes. Meanwhile, place cider and maple syrup in saucepan, and bring to a boil over high heat. Reduce heat to medium, and cook until mixture has reduced to one-third and has a sticky, syrupy consistency, about 15 minutes. Add butter, salt and pepper, and set aside.