01 - Preheat oven to 400°F. Toss butternut squash with 1 tablespoon olive oil, salt, and pepper. Spread on a baking sheet and roast for 20-25 minutes, until tender and lightly caramelized. Reduce oven to 350°F.
02 - While the squash roasts, heat remaining olive oil in a large skillet over medium heat. Add onions and cook until translucent, about 3-4 minutes. Add garlic and cook for another 30 seconds.
03 - Add sausage to the skillet. Cook, breaking up with a spoon, until browned and cooked through. Stir in dried oregano, dried sage, and a pinch of nutmeg. Remove from heat.
04 - Mash roasted butternut squash lightly with a fork, leaving some chunks for texture.
05 - In a bowl, mix ricotta with egg, half the Parmesan, salt, and pepper until well combined.
06 - Lightly oil a 9x13-inch baking dish. Spread 1/2 cup tomato sauce on the bottom. Layer 3-4 noodles over the sauce.
07 - Spread one-third of the ricotta mixture over noodles, add one-third of the sausage mixture, one-third of the butternut squash, a handful of mozzarella, and about 1/3 cup tomato sauce.
08 - Repeat layers twice more: noodles, ricotta, sausage, squash, mozzarella, sauce.
09 - Finish with a final layer of noodles, the remaining sauce on top, and scatter with the rest of the mozzarella and Parmesan.
10 - Cover with foil (sprayed with oil to prevent sticking). Bake at 350°F for 30 minutes.
11 - Remove foil and bake an additional 15-20 minutes until cheese is golden and bubbling. Cool for 10-15 minutes before slicing. Garnish with fresh basil if desired.