Steps
1. Preheat your oven to 375°F (190°C).
2. In a small baking dish, layer the thinly sliced potatoes evenly.
3. In a bowl, whisk together the egg, heavy cream, salt, and pepper. Pour this mixture over the potatoes.
4. Sprinkle the grated Gruyère cheese on top of the potatoes and egg mixture.
5. Bake in the preheated oven for about 30 minutes, or until the potatoes are tender and the top is golden brown.
6. Remove from the oven and let it cool for a few minutes. Garnish with fresh thyme if desired before serving.