Crispy potatoes au gratin are thinly sliced potatoes stacked on their side, instead of layered, for the creamiest potatoes with crispy edges in every bite. A simple make-ahead side dish.Those crispy edges are the best!
Preheat oven to 400º. Butter 2 quart baking dish or a 9 x 5 baking dish.
Combine cheeses and add ⅓ of the cheese mixture to a large bowl.
Add cream, garlic and thyme to the bowl and combine.
Peel and then slice potatoes into ⅛ inch slices with a mandolin, food processor or knife. Add to the bowl and with your hands combine so that each slice is coated with the cream mixture.
Grab a stack and place them vertically in the baking dish, working around the outside first and then going into the center. They should be very tightly packed. Pour any extra cream mixture over the top.
Cover tightly with foil and bake for 30 minutes. Remove foil and continue baking until golden brown, about 30 more minutes. Remove and sprinkle reserved cheese on top and bake until brown and crispy, about 30 more minutes. Total cooking time is 1 ½ hours. Let cool slightly before serving.
Barbara's Notes + Tips
Use russet potatoes for a creamier texture.
You could substitute a mild Swiss cheese for the Gruyere.
Place a pan under the baking dish in case it drips over in the oven.
You can make this in advance, just cover with plastic wrap after you have assembled it in the baking dish and refrigerate. Let it come to room temperature before baking.