01 -
Carefully slice the butternut squash into thin 1/8-inch rounds using a mandolin, spiralizer, or sharp knife. If you're handling a mandolin, think about wearing a cut-proof glove for safety.
02 -
Heat olive oil in a big nonstick pan and break apart the chicken sausage as you cook it. Once browned and fully cooked, toss in the diced onion and garlic, cooking for another 2 minutes until they soften. Stir in the crushed tomatoes, basil, salt, and pepper. Set the heat to low, cover the pan, and let it cook for 15 to 20 minutes.
03 -
Turn the oven on and set it to 375°F (190°C).
04 -
In a bowl, mix together the ricotta cheese, Parmesan, parsley, and egg. Stir it all up until smooth and well blended.
05 -
Spread 3/4 cup of sauce on the bottom of a 9×12-inch deep baking dish. Arrange 12 squash slices to cover it. Put 3/4 cup of the ricotta mixture on top of the squash layer, followed by 1 cup of mozzarella and 1 cup of sauce. Repeat these layers again. For the final top layer, cover with 12 more squash rounds, spread 1 1/2 cups of sauce over them, and wrap the dish tightly with foil.
06 -
Pop the dish into your preheated oven and bake it, covered, for 30 minutes.
07 -
Take off the foil and let it bake for another 30 minutes. This allows the dish to thicken up and remove any extra liquid.
08 -
Sprinkle the rest of the mozzarella cheese on top of the lasagna and bake it for about 5 minutes more—or until the cheese gets beautifully melted and bubbly.
09 -
Once it's out of the oven, let the lasagna sit for 5 to 10 minutes. Slice it evenly into 8 portions and enjoy while it's still warm.