A rich and creamy potato au gratin featuring thinly sliced Yukon Gold or Russet potatoes baked in a flavorful cheese sauce with Gruyère, white cheddar, and Parmesan, perfect as a holiday side dish.
1. Preheat oven to 350°F. Butter a 9x13-inch baking dish.
2. In a small saucepan, heat the half-and-half with Dijon, bay leaf, and thyme until just simmering. Reduce heat and simmer gently for 5–7 minutes. Discard bay leaf and thyme sprigs.
3. While the half and half is warming, melt butter in a skillet over medium heat. Sauté the onion with salt and pepper for 3–4 minutes. Add the garlic and cook until fragrant, 30 seconds.
4. Deglaze with wine and simmer until reduced by half.
5. Add the flour and stir constantly for 1-2 minutes.
6. Gradually whisk in the infused half-and-half, stirring until thickened (3–4 minutes). Season with salt, pepper, and nutmeg.
7. Remove from heat and gradually stir in the Gruyère, white cheddar, and Parmesan, reserving some for topping. Stir until smooth.
8. Layer potatoes in the prepared dish and pour the sauce evenly over the top, making sure all slices are coated.
9. Sprinkle reserved cheeses over the potatoes, cover with foil, and bake for 60–70 minutes. Place another baking sheet or foil beneath the pan to catch any drips.
10. Remove foil and bake 20 more minutes until golden and fork-tender. For extra color, broil at the end for a few minutes.
11. Let rest 10–15 minutes before serving. Garnish with chives and enjoy!
