Ingredients
2 cups heavy cream
4 cups chopped onions
3 cloves peeled garlic, very finely minced/ put through a garlic press
1/4 teaspoon freshly grated nutmeg
1/2 teaspoon dried thyme or 2 teaspoons fresh thyme leaves, chopped
Sea salt and freshly ground white pepper, to taste
10 tablespoons unsalted butter, room temperature
8 lg Yukon Golds, peeled & cut crosswise into 1/8-inch slices
1½ C freshly grated Parmesan with 1/2 C coarsely grated Gruyère
2 cups whole milk
Preparation
Preheat oven to 400 degrees.
In a large saucepan, combine milk, cream, onions, garlic, nutmeg, thyme, salt and pepper. Bring to a simmer. Whisk in 7 tablespoons butter.
Remove pan from heat.
Use remaining 3 tablespoons butter to grease an oval ceramic gratin dish approximately 18 inches in length.
Cover the bottom of the buttered dish with half the potato slices. Season generously with salt and pepper.
Pour half the warm milk mixture over potatoes and then sprinkle with about half of cheese mixture.
Repeat with rest of potatoes, milk mixture and cheese.
Bake in the middle of oven until liquid is absorbed and potatoes are golden and very tender when the tip of a sharp knife is inserted into the center, about an hour or a bit more. Let rest 15 minutes before serving.
