In a broil safe pan, warm olive oil over medium-low heat and then add butternut squash. Sprinkle with salt and pepper, cover, and cook squash 10-12 minutes or until fork tender, adding up to 1/4 cup of water to help steam it, if necessary. Be sure to stir frequently. (Alternatively, you could saute squash for a few minutes, then add 20 minutes of bake time at 350 after assembling the lasagna before broiling to cook it through).
Remove squash from pan and put aside.
Add beef to pan and cook through. Add onions, garlic and spinach; cook until soft. Stir 1/4 cup of sauce to beef mixture.
Add butternut squash back to pan, and flatten beef and veggies down slightly. Top with sauce
Mix one egg, and T of Parmesan cheese into ricotta and sprinkle with fresh ground pepper. Layer ricotta mixture on top sauce.
Finally, top with mozzarella cheese.
Place in your broiler on low for 5-10 minutes or until cheese gets nice and toasty brown. Keep an eye on it, as it happens fast!
Top with extra basil, Parmesan cheese, and sauce if desired.