The decision to employ gratin is not one that should be made lightly. Potatoes are simply the structure needed to absorb the exorbitant amounts of rich heavy cream that supports layers of gooey melted cheese. This dish should be made when you feel like curling up with something blissfully terrible for your body, but perhaps necessary for your spiritual well-being.
Any good melting cheese can be used here, but there’s something magical about how potatoes pair with Brie. Place it in the freezer for 10–15 minutes to make it firm enough to grate easily. Add extra if you’re in the mood to live dangerously.
- 4 extra-large Yukon Gold potatoes, peeled
- 2 tablespoons cornstarch
- 4 ounces Brie, partially frozen
- 4 ounces Gruyère
- 2 leeks, white part only
- 2 tablespoons butter
- 1½ teaspoon kosher salt
- 3 cloves garlic, minced
- 1 tablespoon fresh thyme leaves (can substitute dried leaves)
- 1 teaspoon black pepper
- 1 cup heavy cream
- 1 cup milk
Heat oven to 400°F.
Slice potatoes about ⅛-inch thick. (A mandolin makes this easier). Toss potato slices with cornstarch until coated evenly.
Grate Brie and Gruyère, and set aside.
Cut leeks in half lengthwise, then slice into thin half-moon shapes. Place in bowl of cold water and agitate to remove any dirt. Strain and shake well to remove excess water.
Melt butter in large skillet over medium heat. Add leeks with ⅛ teaspoon kosher salt. Sweat leaks, stirring occasionally, until soft and translucent. Add garlic and thyme. Cook for 3 minutes, or until intensely fragrant. Transfer leek mixture to bowl. Set skillet aside.
Grease gratin pan or 9-by-13-inch casserole dish with butter or cooking spray. Cover bottom with layer of potatoes, overlapping slightly. Season with salt and pepper. Sprinkle half of leeks and a third of the shredded cheese over potatoes, then repeat. Whisk milk and cream together, and pour evenly over gratin. Let rest for 3 minutes so liquid can distribute.
Cover dish with foil. Using sharp knife, cut three 2-inch slits in foil to allow steam to escape.
Put gratin on foil-lined baking sheet. Bake for 30 minutes. Remove foil and bake for another 25–30 minutes, or until the top is golden brown and gratin looks thick and bubbly. Let rest for at least 10 minutes before serving. Serves 4.