Ingredients:
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For the Roasted Garlic:
- 1 head garlic
- 1 tablespoon olive oil
- Salt and pepper
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For the Potato Gratin:
- 2 pounds russet potatoes (about 4-5 medium potatoes)
- 2 tablespoons butter, plus more for greasing the dish
- 1 cup heavy cream
- 1 cup milk
- 1/2 teaspoon dried thyme (or 1 sprig fresh thyme)
- 1/4 teaspoon nutmeg
- 1/2 cup grated Parmesan cheese
- 1 1/2 cups shredded Gruyère cheese (or another shredded cheese like mozzarella)
- Salt and freshly ground black pepper to taste
Instructions:
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Roast the Garlic: Preheat your oven to 375°F (190°C). Using a sharp knife, carefully cut off the top 1/4 inch of the garlic head to expose the cloves. Drizzle the exposed cloves with olive oil, sprinkle with salt and pepper, and wrap the head of garlic in aluminum foil. Place the wrapped garlic on a baking sheet and roast for 30-40 minutes, or until the cloves are very soft and spreadable.
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Prepare the Potatoes: While the garlic roasts, peel the potatoes and thinly slice them using a mandoline (for even slices) or a sharp knife.
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Grease the Baking Dish: Generously butter a 9×13 inch baking dish.
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Make the Creamy Sauce: In a medium saucepan, melt the butter over medium heat. Whisk in the heavy cream, milk, thyme, and nutmeg. Bring to a simmer, then reduce heat and simmer for 5 minutes, stirring occasionally. Season with salt and pepper to taste.
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Assemble the Gratin: Remove the roasted garlic from the oven and let it cool slightly. Squeeze the roasted cloves out of their skins and mash them into a paste with a fork.
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Layer it Up: Spread a thin layer of the creamy sauce in the bottom of the prepared baking dish. Top with a single layer of sliced potatoes. Sprinkle with a mixture of Parmesan and Gruyère cheese, and a bit of the roasted garlic paste. Repeat the layers with remaining potatoes, cheeses, and garlic paste, ending with a cheese layer on top.
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Bake and Enjoy: Pour the remaining creamy sauce over the top of the casserole. Cover the dish tightly with foil and bake for 45 minutes. Remove the foil and bake for an additional 15-20 minutes, or until the potatoes are tender and the top is golden brown and bubbly.
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Let it Rest: Remove the gratin from the oven and let it rest for 10 minutes before serving. This allows the cheese to set and prevents the gratin from being too runny.
Tips:
- For extra flavor, add a pinch of freshly grated nutmeg to the creamy sauce.
- If you don’t have Gruyère cheese, you can substitute another shredded cheese like mozzarella or cheddar.
- Leftovers can be stored in an airtight container in the refrigerator for up to 3 days. Reheat gently in the oven until warmed through.