Preheat oven to 375˚F. Grease a baking dish with 2 tablespoons butter.

Peel potatoes, and, using a mandolin or vegetable slicer, cut into very thin slices.

In a large bowl, combine cream, shredded cheddar, parmesan cheese, garlic, parsley, rosemary, and salt and pepper.

Add sliced potatoes and toss together until all potatoes are well coated. Be careful not to break the thin potato slices.

Working with a small handful of potatoes, gently line up coated slices in the baking dish or skillet. Pour the excess cream mixture over the potatoes.

Add the remaining 2 tablespoons of butter on top of the potatoes. Cover the dish with foil and bake for 40 minutes.

Remove from oven, uncover potatoes and continue to bake for an additional 25 to 30 minutes or until potatoes are tender.