Au Gratin Potatoes
This classic Au Gratin Potatoes recipe delivers restaurant-quality results with tender Yukon Gold potatoes layered in a rich, garlicky cream sauce and topped with a golden, bubbly blend of Gruyere, sharp white cheddar, and Parmesan cheese. Perfected through years of family gatherings, this foolproof recipe uses a simple layering technique and a low-and-slow bake to guarantee creamy centers and a perfectly crispy top every single time.
Equipment
- Mandoline slicer - Set to 1/8-inch (3mm) thickness for uniform slices
- 9x13 inch baking dish - Preferably ceramic or enamel-coated cast iron
- Box grater - Use large holes for shredding cheese
- Large mixing bowl
- Medium saucepan - For making the cream sauce
- Sharp chef's knife
- Measuring cups and spoons
- Aluminum foil
- Oven mitts
- Rimmed baking sheet - To catch any overflow during baking
- Microplane grater - (optional) For freshly grating nutmeg and Parmesan
Ingredients
For the Potatoes
- 3 lbs Yukon Gold potatoes - 1.4 kg, peeled and sliced 1/8-inch thick
- 2 tbsp unsalted butter - divided
- 1 tsp salt
- 1/2 tsp black pepper
- 1/4 tsp nutmeg - freshly grated if possible
For the Cream Sauce
- 2 cups heavy cream - 480 ml
- 1 cup whole milk - 240 ml
- 3 garlic cloves - minced
- 1 tbsp fresh thyme leaves - or 1 tsp dried thyme
- 1 bay leaf
- 1/2 tsp salt
- 1/4 tsp white pepper
For the Cheese Topping
- 2 cups Gruyere cheese - 200g, shredded from a block
- 1 cup sharp white cheddar cheese - 100g, shredded from a block
- 1/2 cup Parmesan cheese - 50g, freshly grated
Instructions
- Preheat oven to 350°F (175°C) with the rack in the center position. Generously butter your 9x13-inch baking dish with 1 tablespoon of butter, coating the bottom and sides completely.
- Mince the garlic, strip the thyme leaves from their stems, and shred all three cheeses using a box grater. Combine the shredded cheeses in a bowl and set aside.
- Set your mandoline to 1/8-inch (3mm) thickness and carefully slice the peeled potatoes into a bowl of cold water to prevent browning. Once all are sliced, drain and pat completely dry with paper towels — removing excess moisture is essential for a creamy, non-watery sauce.
- Combine heavy cream, whole milk, minced garlic, thyme, bay leaf, salt, and white pepper in a medium saucepan over medium heat. Bring to a gentle simmer, then reduce heat and steep for 5 minutes; remove from heat and discard the bay leaf.
- Arrange one-third of the potato slices in an overlapping pattern in the baking dish, season lightly with salt, pepper, and a tiny dash of nutmeg, then pour one-third of the warm cream sauce over the top and sprinkle with one-third of the cheese. Repeat two more times, ending with cheese on top, then dot with the remaining 1 tablespoon of butter cut into small pieces.
- Place the baking dish on a rimmed baking sheet, cover tightly with aluminum foil, and bake for 45 minutes until the potatoes begin to steam and soften.
- Carefully remove the foil and continue baking for 30 more minutes, until the top is golden brown and bubbling and the potatoes are completely tender when pierced with a knife.
- Remove from the oven and let the dish rest for 15 minutes before serving — this allows the cream sauce to thicken and set so each portion holds together. Serve with a large spoon, making sure to include some of the crispy top with each portion.
Notes
- Slice uniformly: A mandoline set to 1/8-inch is the single most important tool for even cooking. Hand-slicing results in uneven thickness and inconsistent doneness.
- Dry the potatoes thoroughly: After rinsing, pat slices completely dry with paper towels. Excess water dilutes the cream sauce and creates a watery final dish.
- Always shred your own cheese: Pre-shredded cheese contains anti-caking agents that prevent smooth melting. Shred from a block for the best results.
- Use warm cream sauce: Adding warm sauce to the layers helps it seep into the potato slices evenly and reduces overall cook time.
- Make-ahead tip: Assemble up to 24 hours in advance, cover tightly, and refrigerate. Remove from the fridge 30 minutes before baking and add 10–15 minutes to the covered bake time.
- Storage: Cool completely, then cover tightly and refrigerate for up to 4 days. To freeze, cut into individual portions, wrap tightly in plastic wrap and foil, and freeze for up to 2 months.
- Reheating: For best texture, reheat covered in a 350°F oven for 20–25 minutes. Add a splash of cream or milk if the potatoes seem dry.
- Cheese swaps: Gruyere is traditional, but you can substitute fontina, Swiss, or smoked gouda. Avoid pre-shredded varieties.
- Potato tip: Yukon Golds are ideal — they hold their shape and have a buttery flavor. Russets work but can become mushier. Avoid waxy red potatoes.
- Classic French variation (Gratin Dauphinois): Omit the cheese entirely and bake with only the cream, garlic, and nutmeg sauce for the traditional preparation.
Nutrition
Serving: 1ServingCalories: 385kcalCarbohydrates: 28gProtein: 12gFat: 26gSaturated Fat: 16gPolyunsaturated Fat: 1gMonounsaturated Fat: 7gCholesterol: 85mgSodium: 495mgPotassium: 620mgFiber: 2gSugar: 3gVitamin A: 18IUVitamin C: 15mgCalcium: 32mgIron: 7mg
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