Preheat oven to 425°. Lightly grease a 2 qt baking dish; set aside. Peel the squash. Slice to 1/4inch thickness. Remove seeds from slices and halve large slices. Arrange onto a cookie sheet tray. Brush both sides lightly with olive oil. Season with salt and pepper. Bake, uncovered, 20 minutes. Remove. Increase oven temperature to 475°.

In a medium saucepan combine cream and cornstarch; cook and stir until thickened and bubbly. Stir in spinach; spread mixture in bottom of prepared dish. Arrange squash over spinach mixture.

In a small bowl stir together Parmesan cheese and crème fraiche. Spread over squash in dish. Bake, uncovered, 10 to 15 minutes or until squash is tender and topping is lightly browned. Season with salt and pepper.

To make crème fraiche. Combine ¼ cup whipping cream and ¼ cup sour cream. Cover with plastic wrap. Let stand at room temperature for 2 to 5 hours or until mixture thickens. When thickened, cover and chill in the refrigerator until serving time or up to 48 hours. Stir before serving.