Creamy Potato and Leek Gratin

From the kitchen of Carly

Tender leeks and paper-thin potato slices get smothered in cream and thyme, then baked until golden and bubbling. This gratin is the kind of side dish that steals the show, rich without feeling heavy, and absolutely worth the knife work.

Prep
n/a
Cook
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Total
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Servings
4
Difficulty
medium

Ingredients

4 servings

  • 19 medium leeks ( about 3 lb; white and pale green parts only)
  • 13 Tbsp unsalted butter
  • 12 lb russet (baking) potatoes
  • 11 1/2 cups heavy cream
  • 11 cup whole milk
  • 12 tsp thyme leaves
  • 1An adjustable-blade slicer

Instructions

  1. Preheat oven to 400°F with rack in middle. Generously butter a 3-qt shallow baking dish. Cut a round of parchment paper to fit just inside a 12-inch heavy skillet, then set parchment aside.

  2. Halve leeks lengthwise, then cut crosswise into 1 1/2-inch pieces (you should have about 8 cups). Wash leeks.

  3. Cook leeks in butter with 1/2 tsp salt and 1/4 tsp pepper, covered with parchment round, in skillet over medium heat, stirring occasionally, until tender, 10 to 12 minutes.

  4. Meanwhile, peel potatoes and slice crosswise 1/16 inch thick with slicer. Transfer to a large heavy pot with cream, milk, thyme, 1 tsp salt, and 1/2 tsp pepper and bring to a boil over medium heat, stirring occasionally (liquid will thicken). Stir in leeks, then transfer to baking dish.

  5. Bake, uncovered, until potatoes are tender, 45 minutes to 1 hour. Let stand 10 minutes before serving.

  6. Gratin can be baked 2 days ahead and chilled. Let stand at room temperature 30 minutes, then reheat, covered, in a 350°F oven until hot, about 30 minutes.