Preheat the oven to 375°F.

Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Add the squash and season with salt and pepper and then pour the water into the skillet. Cover and simmer over medium heat until the squash is fork tender, about 15-20 minutes. You could also cook it in the Instant Pot. Transfer the squash to a food processor. Add the amaretti or biscotti cookies and blend until smooth.

Wipe out your skillet and add the other tablespoon of olive oil over medium heat. Add the mushrooms and sprinkle with ¼ teaspoon kosher salt, and sauté for 8-10 minutes or until soft, stirring occasionally. Remove from pan, wipe out the pan, and set aside.

Heat the pan over medium heat and melt the butter then add the flour and whisk for 1 minute. Whisk in the milk and bring to a gentle boil over medium-high heat, then reduce to medium and simmer until the sauce thickens slightly about 5 minutes. Add the nutmeg and another ¼ teaspoon kosher salt and black pepper. Cool slightly. Transfer half of the sauce to a blender and add the basil. Mixture will be hot so place a towel or cloth over top of blender so the mixture doesn’t explode. Blend until smooth then return the basil sauce to the sauce in the pan and stir to blend. Season with salt and pepper to taste.

Lightly butter a 13 X 9 X 2-inch glass baking dish. Spread ¾ cup of the sauce in the bottom of the prepared baking dish. Arrange a layer of lasagna noodles on the bottom of the pan. Spread ⅓ of the squash puree over the noodles then ⅓ of the mushrooms. Sprinkle with ½ cup of mozzarella cheese and ⅓ cup ricotta cheese. Drizzle ½ cup of sauce over the noodles. Repeat layering 3 more times, ending with a layer of mozzarella and parmesan cheese.

Cover the baking dish with foil sprayed with cooking spray and bake the lasagna for 40 minutes. Remove the foil and bake uncovered for about 15 more minutes or until the top is golden. Remove from oven and let the lasagna stand for 15 minutes before serving.