Rinse, and peel the sweet potatoes, and with a very long and sharp knife, cut the sweet potatoes in 1/8 inch slices, and set aside.
Melt the butter in the microwave, and pour the butter into a large (gallon size) Ziploc bag.
Add the olive oil, Parmesan cheese, Italian seasoning, minced garlic, brown sugar, and thyme, and mix together in the bag.
Place the sweet potatoes in the bag, and zip the bag closed.
Coat the sweet potatoes with the ingredients in the bag (you'll have to move them around in the bag with your fingers, and make sure all the slices are coated).
Place the sweet potatoes in a 9 X 13 dish, lined with parchment paper on the bottom, and lay the slices out in rows, or however, you prefer them (see photo).
Once you've placed all the slices in the dish, remove the remainder of the ingredients left in the bag with a spatula, and top the sweet potatoes with the ingredients.
Sprinkle additional Thyme on top of sweet potatoes in the dish, and place the dish in the oven at 400 degrees, for 40 - 45 minutes, or until the sweet potatoes are golden brown on the edges, and done in the centers.
Remove the dish from the oven to a wire rack to cool for a few minutes before serving.
Serve, and Enjoy!