- Make the mushroom filling. In a large skillet, heat the oil or butter. Add mushrooms and shallots and salt, and sauté 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, then turn the heat off.
- Using a fork, mix the ricotta cheese with the egg, nutmeg and salt.
- Roast squash in 350 F oven for 40 minutes, and when cool add into a food processor. You should have about 4 cups. Add the roasted onion, olive oil, water, salt, pepper and garlic powder. Purée until smooth.
- Assemble the lasagna. In a greased 9 x 13 inch baking dish, add 1 c. of the butternut puree and spread out into a thin layer. Top with lasagna noodles. Add half of the ricotta mixture and spread evenly. Top with half of the cooked mushrooms. Sprinkle with ½ c. grated mozzarella and a couple tablespoons Parmesan cheese.
- Add more lasagna noodles. Spread out the rest of the ricotta mixture as evenly as possible. Spoon half of the remaining butternut purée, erring on the side of less than half, so you have enough to cover the top (save at least 1 ¼ c. for the top.) Add the remaining mushrooms and all the good bits (onions and sage) and sprinkle with another ½ c. shredded mozzarella and couple tablespoons Parmesan.
- Place the final noodles over the top. Layer with the remaining butternut purée and sprinkle with the rest of the cheese.
- 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.
Ingredient availability varies by location*