In a deep nonstick skillet, heat a splash of extra virgin olive oil over medium heat. Add the Italian chicken sausage and cook for about 5 minutes, breaking it apart with a spatula until it browns.

Once the sausage is browned, stir in the chopped onion and minced garlic. Sauté for about 2 minutes or until the onion is translucent and fragrant.

Add the crushed tomatoes and fresh basil to the skillet, seasoning with salt and pepper to taste. Lower the heat and let this mixture simmer on low for 15-20 minutes, covered.

Using a mandolin or a sharp knife, slice the butternut squash into 1/8" thick rounds.

In a mixing bowl, combine the part-skim ricotta, grated Parmigiano Reggiano, chopped parsley, and a large egg. Blend well until smooth and creamy.

In a 9x12 casserole dish, spread a layer of the sausage marinara sauce, then place 12 rounds of butternut squash on top. Follow with a layer of the cheese mixture and a sprinkle of shredded mozzarella. Repeat these layers two more times.

Preheat your oven to 375°F (190°C) and cover the casserole dish with aluminum foil. Bake for 30 minutes, then remove the foil and bake for an additional 30 minutes.

Top the lasagna with the remaining mozzarella cheese and return it to the oven for about 5 minutes, until the cheese is melted and bubbly.