Use a mandolin to thinly slice the potatoes and add to a large bowl.
Cover the potatoes with the cream then add 1 cup of the parmesan cheese and garlic. Season with salt and pepper.
Grease a 9"x 11" (23cm x 28cm) baking dish. Use a slotted spoon to scoop the potatoes into the dish then pour the remaining cream mixture over the top and sprinkle with the remaining Parmesan.
Cover with aluminum foil and bake until the potatoes are fork tender, about 1 hour. Remove the foil and continue baking until the top is golden brown and bubbling, about an additional 15 minutes.
Let cool for about 5 minutes then cut into squares. Use a spatula to serve the dauphinoise potatoes hot.