How to Make Au Gratin Potatoes at Home

What Makes Au Gratin Potatoes Different From Other Potato Dishes

Au gratin potatoes have a specific identity in the cooking world, and understanding what sets them apart helps you make them correctly. The term "au gratin" actually refers to a cooking technique rather than just a flavor profile. It means the dish is topped with breadcrumbs or cheese (or both) and then baked until a golden, crispy crust forms on top. This crust contrasts beautifully with the creamy potato layers underneath.

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The confusion often happens because au gratin potatoes share similarities with scalloped potatoes, but they're not the same thing. Scalloped potatoes are sliced potatoes cooked in a cream sauce without the crispy topping. Au gratin potatoes require that finished crust to earn their name. Some recipes use only breadcrumbs, others use only cheese, and many recipes use both together. The choice depends on whether you want a heavier, more luxurious dish (with cheese) or a lighter version with more textural contrast (with breadcrumbs).

The dish has French origins, though it's become popular in American home cooking and appears on restaurant menus across different cuisines. The creamy potato base typically uses heavy cream or a cream sauce made from butter, flour, and milk—a béchamel sauce. The cheese layer (usually Gruyère, cheddar, or Parmesan) melts into this cream, creating the rich flavor people expect. The baking process—usually 40 to 60 minutes in a 350-375°F oven—allows the potatoes to become tender while the top browns and crisps.

Practical takeaway: Before you start cooking, decide what kind of au gratin potatoes you want to make. Do you want a heavier, cheesier version for a special occasion, or a lighter side dish with more textural variety? This decision affects how you'll layer and season your dish.

Selecting and Preparing Your Potatoes Correctly

The type of potato you choose matters more than many cooks realize. Starchy potatoes like russets are not ideal for au gratin because they break down too easily during cooking, turning mushy. Instead, you want waxy or medium-starch potatoes that hold their shape. Red potatoes, Yukon golds, and fingerlings are excellent choices. These varieties have less starch and more moisture, which means they stay firm during the long baking process. If you can only find russets, that's workable, but you'll need to be careful not to overcook them.

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How you size and cut your potatoes affects cooking time and final texture. Thin, uniform slices cook evenly and allow the cream sauce to penetrate throughout the dish. Most recipes call for slices between 1/8 inch and 1/4 inch thick. A mandoline slicer makes this easier and more consistent, though a sharp knife works fine if you're careful. Consistency matters because thick slices will still be crunchy inside while thin slices turn to mush. Aim for that middle ground.

Rinsing your sliced potatoes is an optional but worthwhile step. Cutting potatoes releases starch on the surface. Rinsing them briefly under cold water removes some surface starch, which can make the final dish slightly creamier and less gluey. You don't need to soak them—just a quick rinse and pat dry with paper towels works. Some cooks skip this step entirely, and au gratin potatoes turn out fine, but rinsing can improve the texture slightly.

The amount of potatoes you use depends on your baking dish size. A standard 9-by-13-inch baking dish holds about 2 to 2.5 pounds of potatoes. Weigh them if you have a scale, or count on about 5 to 7 medium potatoes. The potatoes should fill the dish comfortably without overflowing, with enough room for the cream sauce to distribute throughout. If you pack too many potatoes in, they won't cook evenly. If you use too few, the dish will be mostly sauce with a watery texture.

Practical takeaway: Buy waxy potatoes like Yukon golds or reds, slice them uniformly between 1/8 and 1/4 inch thick, give them a quick rinse, and pat them dry. This preparation takes about 10 to 15 minutes and sets you up for success.

Making the Cream Sauce Base That Holds Everything Together

The cream sauce is what transforms sliced potatoes into au gratin potatoes. This sauce is typically a béchamel—a classic French sauce made from butter, flour, and milk. You can also make a richer version using heavy cream instead of some or all of the milk. The ratio is usually 3 tablespoons of butter, 3 tablespoons of flour, and 2 cups of milk or cream. This makes enough sauce for a standard 9-by-13-inch baking dish with 2 pounds of potatoes.

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The technique for making béchamel is straightforward but requires attention. Melt butter over medium heat in a saucepan. Once the butter is foaming, add flour and stir constantly for about 1 to 2 minutes. This cooking time lets the flour cook slightly and removes the raw flour taste. This mixture is called a roux. Then slowly add your milk, whisking constantly to prevent lumps. If you pour all the milk in at once, you'll get clumps that are difficult to remove. Whisking as you pour prevents this. The sauce will thicken as it heats, taking about 5 to 10 minutes to reach a consistency that coats the back of a spoon.

Seasoning the sauce is where flavors develop. Salt and black pepper are essential—use about 3/4 teaspoon of salt and 1/4 teaspoon of pepper, though you may adjust this based on your taste. Many cooks add a pinch of nutmeg to béchamel, which is a traditional French touch that adds subtle warmth without making the dish taste like pumpkin pie. Some recipes include garlic powder, cayenne, or fresh thyme. If you're adding cheese to the sauce (rather than just on top), add it at the end, off the heat, so it melts smoothly without breaking. Gruyère, sharp cheddar, and Parmesan all work well. Use about 1 to 1.5 cups of cheese mixed into the sauce.

Temperature matters for this step. Keep your heat at medium, not high. High heat can make the milk scorch on the bottom, creating a burnt taste. If your sauce seems too thick, thin it with a bit more milk. If it's too thin, cook it a little longer—the starch in the flour will continue to absorb liquid and thicken the sauce. The final sauce should pour easily but coat the back of a spoon. It will thicken slightly more as it cools before you pour it over the potatoes.

Practical takeaway: Make your sauce about 15 minutes before you're ready to assemble the dish. This gives it time to cool slightly and reach the right consistency. Keep it smooth by whisking constantly as you add milk, and don't skip the seasoning—this sauce is where most of the flavor comes from.

Assembling and Layering for Even Cooking

How you layer the potatoes and sauce affects both the cooking and the final texture. Start by preparing your baking dish—a 9-by-13-inch ceramic or glass dish works well, though metal works too. Lightly butter or oil the bottom of the dish to prevent sticking. Some cooks also sprinkle a thin layer of grated cheese on the bottom, which adds flavor and prevents sticking.

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Layer your potatoes and sauce in alternating layers, starting with potatoes. Arrange a single layer of potato slices on the bottom of the dish, overlapping them slightly like roof shingles. This overlapping pattern helps them stay submerged in the sauce and cook evenly. Once you've covered the bottom, pour about 1/3 of your sauce over this layer. Then add another layer of potatoes, another pour of sauce, and repeat until you've used all your potatoes and sauce. Your top layer should be sauce, not potatoes. This ensures the top potatoes stay moist during cooking.

If you're adding cheese on top