01 -
Set oven to 350°F and position rack in the center.
02 -
Grate both cheddar and parmesan cheese. Peel potatoes and slice them evenly into 1/8 inch rounds using a mandoline slicer.
03 -
Melt butter in a small saucepan over medium-high heat. Add minced garlic; sauté for 30 seconds. Stir in cream, salt, and pepper, warming gently. When mixture starts to simmer, remove from heat.
04 -
Grease a 9x13 inch baking dish. Arrange half the sliced potatoes in the dish with slight overlap. Pour half the cream mixture over the potatoes. Sprinkle half of each cheese on top. Repeat with remaining potatoes, cream mixture, and remaining cheeses.
05 -
Cover dish tightly with foil and bake for 40 minutes. Remove foil and bake an additional 25 to 35 minutes until potatoes are tender when pierced with a toothpick and the cheese is golden brown. Oven times may vary; check doneness earlier if needed.