Preheat your oven to 400 degrees F.
Peel the sweet potatoes and cut them into slices. Lightly butter a large rectangular or oval baking dish.
Arrange the sweet potato slices in the dish by stacking them together, then fan them out around the edges and into the center of the baking dish.
In a small bowl, whisk together the oil, melted butter, garlic, 1/2 cup of Parmesan cheese, and Italian seasoning until well combined.
Pour the mixture over the sweet potatoes in the baking dish, making sure they are evenly coated.
Evenly sprinkle the remaining 1/4 cup of parmesan cheese on top. Cover the dish with tin foil and bake for 1 hour.
After 1 hour, remove the dish from the oven, remove tin foil and bake for an additional 15 minutes. Sweet potatoes are done when they can be easily pierced with a fork.
Serve warm, and garnish with fresh thyme. Bon Appetit!