Preheat the oven to 400°F.

Spray a 9x13-inch baking dish with nonstick cooking spray.

Peel the butternut squash. Cut it in half lengthwise and remove the seeds. Slice each half crosswise into scant 1/4-inch slices.

Arrange the butternut squash slices in the casserole dish so that they are slightly overlapping. Sprinkle with salt and black pepper. Pour the heavy cream evenly over the squash. Sprinkle with minced garlic, fresh thyme leaves, and nutmeg.

Place the breadcrumbs, Parmesan cheese, and salt in a mixing bowl. Pour the melted butter over the bread crumbs and mix with a large fork until all the crumbs are moistened.

Sprinkle the breadcrumb mixture evenly over the squash.

Bake the casserole on middle rack of oven until the squash is tender and bubbling at the edges and the topping is crisp and golden brown, 30-35 minutes.

Check to see that casserole is done. Remove from oven or add time as needed.

Allow the casserole to rest for 10 minutes before serving.