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A golden brown casserole of creamy Scalloped Potatoes Au Gratin, topped with melted cheese and fresh herbs, sits on a kitchen counter.

Ultimate Scalloped Potatoes Au Gratin

This is the ultimate recipe for Scalloped Potatoes Au Gratin, featuring layers of tender Yukon Gold potatoes baked in a rich, velvety sauce of heavy cream, Gruyère, and Parmesan. The dish is crowned with a spectacularly golden, crispy crust and requires a crucial resting period for perfect, clean slices. It's a luxurious and comforting side dish that elevates any meal.
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Prep Time 30 minutes
Cook Time 1 hour 20 minutes
Total Time 1 hour 50 minutes
Servings: 8
Course: Side Dish
Cuisine: American, French
Calories: 450
Ingredients Equipment Method Notes

Ingredients
  

  • 3 cups heavy cream
  • 3 cloves garlic, minced
  • 1 1/2 tsp kosher salt
  • 1/2 tsp freshly ground black pepper
  • 1/4 tsp freshly grated nutmeg
  • 1 tbsp unsalted butter, softened
  • 1 tbsp fresh thyme leaves or 1 tsp dried

Equipment

  • 9x13 inch (3-quart) baking dish
  • Sharp Knife or Mandoline
  • Large bowl
  • Medium saucepan
  • Measuring cups and spoons
  • Box grater
  • Kitchen towels
  • Aluminum foil
  • Paring knife

Method
 

  1. Preheat oven to 375°F (190°C). Generously grease a 9x13 inch baking dish with the softened butter.
  2. Slice the unpeeled potatoes uniformly to 1/8-inch thickness using a sharp knife or mandoline. Place slices in a large bowl of cold water to prevent browning.
  3. Grate the Gruyère and Parmesan cheeses. Set aside.
  4. In a medium saucepan, combine heavy cream, minced garlic, salt, pepper, and nutmeg. Warm over medium heat until it just begins to simmer at the edges. Do not boil. Remove from heat.
  5. Drain the potato slices and pat them very dry with clean kitchen towels.
  6. Arrange a single, slightly overlapping layer of potatoes in the bottom of the prepared dish. Sprinkle lightly with a pinch of thyme.
  7. Ladle a portion of the cream mixture evenly over the potatoes, then sprinkle with a handful of the mixed cheeses.
  8. Repeat the layering process (potatoes, thyme, cream, cheese) until all ingredients are used, finishing with a final layer of cream and a generous topping of the remaining cheese.
  9. Cover the dish tightly with aluminum foil and bake on the middle rack for 45 minutes.
  10. Remove the foil (the dish will be liquidy). Increase oven temperature to 400°F (200°C) and bake, uncovered, for 25-35 minutes, until the top is golden brown and the sauce is bubbling thickly.
  11. Remove from oven and let the gratin rest for at least 20 minutes before serving to allow the sauce to set.

Notes

For best results, use freshly grated cheese as pre-shredded contains anti-caking agents that can affect sauce texture. To test for doneness, a paring knife should easily pierce the potatoes before removing the foil. The dish can be assembled, covered, and refrigerated up to 24 hours in advance; let sit at room temperature for 30 minutes before baking and potentially add 5-10 minutes to the covered baking time. For flavor variations, try adding a layer of caramelized onions or crispy chopped bacon between the potato layers.