3 pounds baking potatoes, like russets, peeled and thinly sliced, (vertically)
1 pound Gruyere, grated
Preheat the oven to 400 degrees F.
In a mixing bowl, whisk the cream and yolks together. Whisk well. Season with salt and pepper. Butter a square-baking dish.
Lay a layer of the potatoes over the bottom of the pan. Season the layer with salt and pepper. Sprinkle with an eighth of the cheese. Ladle 1 cup of the cream mixture over the cheese. Lay another layer of the potatoes over the cream mixture. Using your hands, firmly press the layers together. Repeat the above process with the remaining ingredients.
Place a piece of parchment paper over the potatoes and cover with foil. Place in the oven and cook for 30 minutes. Remove the foil and continue to cook for 15 minutes. Remove from the oven and cool completely. Reheat and slice into individual servings.