Follow these steps to create your Butternut Squash and Spinach Lasagna:

1. Preheat Oven: Preheat your oven to 375°F (190°C). This ensures even cooking of the lasagna.

2. Cook Noodles: Bring a large pot of salted water to a boil. Add the lasagna noodles and cook until al dente according to package instructions. Drain and set aside.

3. Prepare Butternut Squash: In a large skillet, heat olive oil over medium heat. Add the diced butternut squash and sauté for about 10 minutes until tender. Stir in chopped onions and garlic, cooking until the onions are translucent.

4. Add Spinach: Mix in the fresh spinach, cooking until wilted. Season the mixture with thyme, oregano, salt, and pepper. Remove from heat and let it cool slightly.

5. Make the Ricotta Mixture: In a bowl, combine ricotta cheese, half of the mozzarella, and Parmesan cheese. (If using, add the egg to the mixture for extra creaminess.) Stir well to combine.

6. Assemble the Lasagna: In a 9×13 inch baking dish, spread a thin layer of marinara sauce on the bottom. Place three lasagna noodles over the sauce. Spread half of the ricotta mixture over the noodles, followed by half of the butternut squash and spinach mixture, then a layer of marinara sauce. Repeat the layers, finishing with noodles on top.

7. Top with Cheese: Spread the remaining marinara sauce over the top layer of noodles. Sprinkle the remaining mozzarella cheese over the sauce.

8. Cover and Bake: Cover the dish with aluminum foil, making sure it doesn’t touch the cheese. Bake in the preheated oven for about 30 minutes.

9. Uncover and Finish Baking: Remove the foil and bake for another 15 minutes until the cheese is bubbly and golden brown.

10. Let It Set: Once done baking, allow the lasagna to sit for about 10 minutes before slicing to help it hold its shape when served.