Herbed Potato Gratin

Preheat an oven to 375°F (190°C). Butter an 11-inch (28-cm) gratin dish.

In a large saucepan over medium heat, combine the cream, garlic, rosemary, thyme, sage and a pinch each of salt and pepper. Bring just to a boil, then remove from the heat and set aside.

Peel the potatoes. Using a mandoline or very sharp knife, cut the potatoes into slices about 1/8 inch (3 mm) thick. Gently stir the potato slices into the cream mixture.

Arrange one-third of the potato slices, slightly overlapping, on the bottom of the prepared dish. Sprinkle generously with salt and pepper, half of the onions and 1 cup (125 g) of the Gruyère. Repeat, using another one-third of the potato slices, salt and pepper, all the remaining onions, and another 1 cup (125 g) of the Gruyère. Top with the remaining potatoes and sprinkle with salt and pepper again. Using a large, flat spatula, gently press on the potatoes to compact them. Pour any cream mixture remaining in the saucepan over the potatoes and sprinkle evenly with the remaining 1 cup (125 g) Gruyère and the Parmesan.

Cover the dish with aluminum foil and bake until the potatoes are tender when pierced with a sharp knife, about 45 minutes. Remove the foil and bake until the gratin is golden brown and bubbly, about 20 minutes more. Let the gratin rest for 10 minutes, then use a spatula to cut it into squares and serve immediately. Serves 6 to 8.

Williams-Sonoma Test Kitchen