Potatoes au Gratin

• servings: 12 servings

Ingredients

5 garlic cloves, divided

1 Tbsp. unsalted butter, room temperature

2 medium shallots, quartered through root ends

2½ cups heavy cream

1 Tbsp. Diamond Crystal or 1¾ tsp. Morton kosher salt

1 tsp. freshly ground black pepper

1 Tbsp. thyme leaves, plus more for garnish

4 lb. russet potatoes, scrubbed, very thinly sliced on a mandoline

3 oz. Gruyère, finely grated

1 oz. Parmesan, finely grated

Directions

Preheat oven to 325°. Cut 1 garlic clove in half and rub the cut sides all over the inside of a 3-qt. shallow baking dish. Smear 1 Tbsp. unsalted butter, room temperature, all over inside of dish. Bring 2 medium shallots, quartered through root ends, 2½ cups heavy cream, 1 Tbsp. Diamond Crystal or 1¾ tsp. Morton kosher salt, 1 tsp. freshly ground black pepper, 1 Tbsp. thyme leaves, and remaining 4 garlic cloves to a simmer in a small saucepan over low heat; cook until shallots and garlic are very soft, 15–20 minutes. Let cool slightly. Transfer to a blender; blend until smooth.

Arrange 4 lb. russet potatoes, scrubbed, very thinly sliced on a mandoline, in prepared dish, fanning out a handful at a time and placing in dish at an angle (this ensures every scoop will have tender potatoes from the bottom and crispy edges from the top). Shingle sliced potatoes as you work until bottom of dish is covered. Tuck smaller slices into any gaps to fill. Pour cream mixture over potatoes and cover dish tightly with aluminum foil. Bake potatoes until tender and creamy, 60–75 minutes. Let cool.

Place rack in highest position; heat broiler. Remove foil and top potatoes with 3 oz. Gruyère, finely grated, and 1 oz. Parmesan, finely grated. Broil until cheese is bubbling and top of gratin is golden brown, 5–10 minutes. Serve topped with more thyme leaves. Do ahead: Gratin can be baked 1 day ahead. Cover and refrigerate. Bring to room temperature before broiling. Editor’s note: This potato gratin recipe was first printed in October 2015. Head this way for more of our favorite Christmas dinner ideas →