📝 About This Recipe
This quintessential French comfort dish elevates humble root vegetables into a decadent masterpiece of textures and flavors. Layers of buttery, melt-in-your-mouth Yukon Gold potatoes are interlaced with silkily sautéed leeks and bathed in a luxurious, nutmeg-scented cream. Finished with a golden, bubbling crust of cave-aged Gruyère, this gratin is the ultimate side dish for a celebration or a cozy Sunday roast.
🥗 Ingredients
The Vegetables
- 3 pounds Yukon Gold potatoes (peeled and sliced into 1/8-inch thick rounds)
- 3 large Leeks (white and light green parts only, cleaned and thinly sliced)
- 3 tablespoons Unsalted butter (plus extra for greasing the dish)
- 3 cloves Garlic (1 clove halved for rubbing, 2 cloves minced)
The Cream Infusion
- 2 cups Heavy cream (at room temperature)
- 1/2 cup Whole milk
- 2 teaspoons Fresh thyme (leaves only, finely chopped)
- 1/4 teaspoon Ground nutmeg (freshly grated is best)
- 2 teaspoons Kosher salt (plus more for the leeks)
- 1/2 teaspoon Black pepper (freshly cracked)
The Topping
- 1.5 cups Gruyère cheese (freshly shredded)
- 1/4 cup Parmigiano-Reggiano (finely grated)
- 2 tablespoons Fresh chives (finely snipped for garnish)
👨🍳 Instructions
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1
Preheat your oven to 375°F (190°C). Rub the inside of a 9x13 inch ceramic baking dish with the cut side of a garlic clove, then grease generously with butter.
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2
In a large skillet over medium heat, melt 3 tablespoons of butter. Add the sliced leeks and a pinch of salt.
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3
Sauté the leeks for 8-10 minutes until they are soft, translucent, and just beginning to turn golden. Add the minced garlic and cook for 1 minute more until fragrant.
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4
In a medium saucepan, combine the heavy cream, milk, chopped thyme, nutmeg, salt, and black pepper. Heat over low until warm but not boiling.
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5
Slice your peeled potatoes using a mandoline or a very sharp knife to ensure they are uniform 1/8-inch thick rounds. Do not rinse them after slicing; the starch helps thicken the sauce.
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6
Arrange one-third of the potato slices in the bottom of the prepared baking dish, overlapping them slightly like shingles.
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7
Spread half of the sautéed leek mixture evenly over the first layer of potatoes.
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8
Repeat with another layer of potatoes, the remaining leeks, and a final layer of potatoes on top.
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9
Carefully pour the warm cream mixture over the potatoes. Use a spatula to gently press down on the potatoes to ensure the cream seeps into every layer.
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10
Cover the dish tightly with aluminum foil. Place the dish on a rimmed baking sheet to catch any drips.
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11
Bake for 45 minutes. Remove the foil and check if the potatoes are tender by piercing with a knife; they should offer little resistance.
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12
Sprinkle the shredded Gruyère and Parmigiano-Reggiano evenly over the top.
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13
Return to the oven, uncovered, for another 20-25 minutes until the top is bubbling and a deep golden brown.
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14
Remove from the oven and let the gratin rest for at least 15 minutes. This is crucial as it allows the sauce to thicken and the layers to set.
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15
Garnish with fresh chives and serve warm from the dish.
💡 Chef's Tips
Use Yukon Gold potatoes because they hold their shape better than Russets while providing a buttery texture. Clean leeks thoroughly by soaking sliced rounds in cold water to remove any hidden grit or sand. Don't skip the resting period; if you cut into it too early, the cream sauce will be runny. If the top browns too quickly before the potatoes are soft, tent it loosely with foil for the remainder of the bake. For a lighter version, you can substitute half of the heavy cream with whole milk, though it won't be as rich.
🍽️ Serving Suggestions
Serve alongside a roasted beef tenderloin or a herb-crusted rack of lamb. Pair with a crisp, dry white wine like a French Chablis or a Sauvignon Blanc to cut through the richness. A simple green salad with a sharp lemon vinaigrette provides a perfect acidic balance to the creamy gratin. Accompany with roasted balsamic Brussels sprouts for a complete autumnal feast.