Instructions

1. Preheat the oven to 375°F (190°C). Grease a 9x13 inch baking dish with butter.
2. In a medium saucepan, combine the heavy cream and minced garlic. Heat over medium heat until the mixture begins to simmer, then remove from heat and set aside to infuse the garlic flavor.
3. In the prepared baking dish, layer half of the sliced potatoes evenly across the bottom. Season with salt, pepper, and half of the chopped thyme.
4. Pour half of the heated cream mixture over the first layer of potatoes, ensuring even coverage.
5. Sprinkle half of the grated Gruyere and Parmesan cheese over the potato layer, ensuring good distribution.
6. Repeat the layering process with the remaining sliced potatoes, the remaining cream mixture, the rest of the cheese, and thyme, finishing with a generous layer of cheese on top.
7. Melt the remaining butter and drizzle it evenly over the top layer of cheese to enhance the richness.
8. Cover the baking dish with aluminum foil and bake in the preheated oven for 40 minutes.
9. After 40 minutes, carefully remove the foil and bake for an additional 20 minutes, or until the potatoes are tender and the top is golden and bubbly.
10. Allow the potato gratin to cool for 5-10 minutes before serving to let the layers set.