START THE BUTTERNUT. Preheat oven to 425 F. Cut butternut squash in half, scoop out the seeds and place open side down on a parchment-lined baking sheet. Place sliced onion next to it and drizzle it with a little olive oil. Roast until fork-tender, about 30-40 minutes. Let cool. You could do this a day before or cook whole in an instant pot for 22 minutes.

Lower oven to 375F

Make the mushroom filling. In a large skillet, heat the oil or butter. Add mushrooms and shallots and salt, and saute over medium heat, until the mushrooms release their liquid and begin to brown. Add the garlic, sage and pepper.  Cook until garlic is fragrant, about 2-3 more minutes, turn the heat off. You could toss in some spinach at the end and wilt for extra nutrients. Taste and make sure the filling has enough salt and pepper. You could also add a little truffle oil. You could make this 1-3 days ahead and refrigerate.

Using a fork, mix the ricotta cheese with the egg, nutmeg and salt. ( You really don’t have to add the egg, but it adds a nice richness.)

Make the BUTTERNUT SAUCE: When the butternut is cool enough to handle, scoop all the flesh out into a food processor. You should have about 4 cups. Add the roasted onion, olive oil, water, salt, pepper and garlic powder. Puree until smooth. You will need at least 3 1/2  cups pureed and you want it to be almost saucy, like a marinara sauce ( so add water if need be!). This will act as the “sauce”.

Assemble the lasagna. In a greased 9 x13 inch baking dish, add 1 cup of the butternut puree and spread out into a thin layer. Top with  lasagna noodles. Add ½ of the ricotta mixture and spread out evenly. Top with half of the cook mushrooms. Sprinkle with ½ cup grated mozzarella and a couple tablespoons romano cheese. Add more lasagna noodles. Spread out the rest of the ricotta mixture as evenly as possible. Spoon half of the remaining butternut puree, erring on the side of less than half, so you have enough to cover the top (save at least 1 ¼ cups for the top.) Add the remaining mushrooms and all the good bits ( onions and sage) and sprinkle with another ½ cup shredded mozzarella and couple of tablespoons parmesan. Place the final noodles over the top. Lather with the remaining butternut puree and sprinkle with the rest of the cheese ( or make the creamy béchamel sauce.- See notes.) You could assemble this 1-2 days before baking.

Cover tightly with foil and bake in 375 F oven for 40 minutes. (If the foil touches the lasagna, place a layer of parchment between the foil and lasagna). Uncover and continue baking 15-20 minutes until golden and bubbly. Cut into 9 servings.

Garnish with optional crispy sage leaves.