Preheat oven to 375 degrees. Set goat cheese on the counter and let it soften at room temperature.
Spray a 3-4 quart casserole dish with with non-stick spray.
Peel the sweet potatoes and cut into slices about 1/4 inch thick. (Don’t make them too thick or they will take longer to cook.) I use my madoline to do this.
Add the softened goat cheese to a bowl along with the half and half and the thyme. Whisk together until smooth. (You can put the goat cheese in the microwave and heat in 10 second intervals until it’s soft to make this easier to mix.)
Place half of the the sweet potatoes in the baking dish. Season with salt and pepper. Spread half the goat cheese mixture over the sweet potatoes. Then sprinkle on half the grated Parmesan.
Layer the remaining sweet potatoes in the dish and season with salt and pepper. Spread the remaining goat cheese mixture over the potatoes and sprinkle with the remaining Parmesan cheese.
Cover the dish tightly with foil. Bake for 1 hour at 375 degrees (or until the sweet potatoes are quite soft when you stick a fork in them.)
Remove foil and bake 20 minutes more, until the sweet potatoes are very soft and the top is nicely browned. Serve hot.