Ordinary potatoes become a sensational side dish when baked in a rich mixture of cream, crème fraîche and nutty Gruyère cheese. A drizzle of truffle oil at the end adds an aromatic touch, making this a dish worthy of a holiday feast.
Truffle Potato Gratin
- 2 lb. (1 kg) Yukon Gold potatoes
- Kosher salt and freshly ground pepper
- 1 Tbs. extra-virgin olive oil
- 1 Tbs. white truffle oil, plus more for drizzling
- 1 yellow onion, diced
- 1 1/2 cups (12 fl. oz./375 ml) heavy cream
- 1 cup (4 oz./125 g) shredded Gruyère cheese
- 1/2 cup (4 oz./125 g) crème fraîche
- Finely chopped fresh thyme for garnish (optional)
1. Preheat an oven to 400°F (200°F). Butter a gratin dish or 9-inch (23-cm) square baking dish.
2. Using a mandoline or a very sharp knife, cut the potatoes into slices about 1/8 inch (3 mm) thick. Arrange the potato slices, slightly overlapping, on the bottom of the prepared dish. Sprinkle lightly with salt and pepper.
3. In a saucepan over medium heat, warm the olive oil and truffle oil. Add the onion to the pan and sauté until tender, about 4 minutes. Add the cream and bring to a simmer. Simmer, stirring occasionally, until thickened slightly, about 5 minutes. Stir in 3/4 cup (3 oz./90 g) cup of the cheese and cook, stirring, until melted. Remove the mixture from the heat and stir in the crème fraîche. Season with salt and pepper.
4. Pour the cream mixture evenly on top of the potatoes and sprinkle the remaining 1/4 cup (1 oz./30 g) cheese evenly on top. Bake until the mixture is golden brown and bubbly and the potatoes are tender when pierced with a sharp knife, about 1 hour. Let the gratin rest for about 15 minutes. Drizzle lightly with more truffle oil, garnish with thyme and serve immediately. Serves 6 to 8.
Williams Sonoma Test Kitchen