Add the cooked butternut squash to a blender or food processor. (I'm using frozen butternut squash cubes so I just microwave it) Add in the butter, cream, salt, pepper, garlic powder, and sage. Blend until smooth and creamy.

In a large skillet over medium-high heat, brown the Italian sausage, breaking it into small crumbles as it cooks.

Add the minced garlic, Italian seasoning, and sage. Cook for another minute until fragrant.

Add the fresh spinach and cook for 2–3 minutes, stirring until wilted. If using red pepper flakes, stir them in. Remove from the heat and set aside.

Tip: If you like the lasagna to be meaty double the ingredients for sausage layer.

Make the cheese béchamel sauce. In a medium saucepan, melt the butter over medium heat. Whisk in the flour and cook for about 1 minute.

Slowly pour in the milk, whisking continuously to prevent lumps. Continue cooking for 5–7 minutes, stirring frequently, until the sauce thickens enough to coat the back of a spoon.

Season with salt, pepper, garlic powder, and optional nutmeg.

Remove from the heat and stir in the mozzarella and Parmesan until melted and smooth. The sauce should be creamy and pourable, not overly thick. If needed, whisk in a little extra milk.

Preheat the oven to 375°F. Lightly grease a 9x13-inch baking dish.

Spread a thin layer of béchamel sauce over the bottom of the baking dish, about 1/2 cup.

Layer the ingredients in this order: A layer of lasagna noodles. One-third of the butternut squash mixture. One-third of the sausage and spinach mixture. A generous layer of béchamel sauce.

Repeat these layers two more times, finishing with a final layer of lasagna noodles.

Spread the remaining béchamel sauce evenly over the final noodle layer. This is important for keeping the top noodles moist! Sprinkle mozzarella and Parmesan over the top.

Cover the baking dish tightly with foil and bake for 1 hour if using the oven ready lasagna noodles or 30 minutes if your noodles are already cooked.

Remove the foil and bake for another 5-10 minutes, until the cheese is melted, lightly golden, and the lasagna is bubbling around the edges. If you'd like a golden brown top turn the oven to broil for a couple of minutes. Just watch the cheese doesn't burn.

Let the lasagna rest for 15 minutes before slicing and serving. This helps the layers set so you get nice slices.