Preheat your oven to 400℉.

Bring a large pot of salted water to a boil. Par cook the lasagna noodles (about 2 minutes less than the package directions). Once cooked, drain the water, dry off the noodles a bit and set them aside.

Spread out the butternut squash cubes on a large baking sheet. Drizzle them with olive oil and sprinkle with salt and pepper. Roast for about 30 minutes, until tender. 

Once the butternut squash is done roasting and cooled off a little bit (to room temp) add it to a blender with the whole milk, nutmeg, cinnamon, and a pinch of salt and pepper. Blend until smooth, then stir in ¼ cup of the ricotta cheese. 

In a separate bowl, combine the remaining ricotta cheese, egg, spinach, parmesan cheese, mozzarella cheese, and a pinch of salt and pepper. 

In a greased (butter or non-stick spray) 9x13 baking dish, begin to layer your lasagna.

Start on the bottom of the dish with a thin layer of the butternut squash sauce mixture

Layer 3 noodles

Then add a layer of the butternut squash mixture

Then add a layer of the ricotta and spinach mixture

Continue this pattern (noodles, squash, cheese) until you're out of the ingredients. Should be  4 layers of noodles. Cover with aluminum foil and bake at 375℉ for 30 minutes covered, then 10 minutes uncovered. If you're looking for a nice bubbly browned top, broil for an additional 5 minutes. 

Serve with thyme springs (if desired).