Au Gratin Potatoes

Making au gratin potatoes from scratch is easier than you might think! One of the all-time classic potato recipes, potatoes au gratin combines simple ingredients—thinly sliced uncooked potatoes, onions and a rich cheese sauce—that’s baked until lightly browned and bubbly. It’s a winner at any dinner table, party or potluck.

Serve au gratin potatoes alongside just about main, from sugar-glazed ham for the holidays to fried chicken or with your favorite meat loaf recipes.

Au Gratin vs. Scalloped Potatoes

If you’re wondering what the difference is between scalloped and au gratin potatoes, the simple answer is cheese. While both dishes feature thinly sliced potatoes baked in a cream sauce until golden brown, traditionally only au gratin potato recipes include cheese. Afterall, the word gratin is a French cooking term for any dish topped with cheese or buttery bread crumbs popped in the oven or under a broiler until brown and crispy.

However, while often made only with heavy cream or milk and a roux, many scalloped potato recipes today also include cheese. And honestly, we’re okay with that.

Ingredients for Au Gratin Potatoes

• Potatoes: When it comes to the types of potatoes to use for au gratin potatoes, russet potatoes (also referred to as Idaho potatoes), are ideal for this recipe. They’re high in starch and soak up the sauce as they cook, yet retain their shape. Yukon gold potatoes can also be used in this recipe. Avoid red potatoes, which are lower in starch and are likely to fall apart while cooking.
• Flour and butter: The base of this recipe’s rich cheese sauce is a roux made from butter, flour, salt and pepper. When combined with the milk and cheese, the roux thickens the sauce.
• Cheese: For best results, freshly grate the cheddar from a block of cheese. Prepackaged cheese can be used in a pinch (these are our Test Kitchen’s picks for the best shredded cheddar cheese), but it won’t melt as smoothly. Gruyère, Swiss or provolone are tasty alternatives.
• Milk: This recipe calls for 2% milk. However, if you’re feeling extra decadent, half-and-half or even heavy cream are great alternatives.
• Onion: A white or yellow onion will do. If even the thought of chopping onions brings tears to your eyes, our Test Kitchen’s suggestions on how to cut an onion without crying, including wearing goggles (but a very sharp knife will do).

Special Equipment

• Mandoline: A mandoline slicer will make quick work of slicing the potatoes.

Directions

Step 1: Make the cheese sauce

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Preheat oven to 350°F. In a large saucepan, melt the butter over low heat. Stir in flour, salt and pepper until smooth. Gradually add the milk, stirring to ensure there are no lumps. Bring to a boil. Cook and stir for 2 minutes or until thickened. Remove from the heat.

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Stir in the cheese until melted.

Editor’s Tip: Cooking the roux just long enough eliminates the taste of raw flour, but you don’t want to take it too far. After you add the flour and seasonings to the butter, stir until the mixture looks bubbly and foamy, and then it should look like a thick paste. Using a whisk is fine, but consider using a rubber spatula to make sure the mixture doesn’t collect in the corners and burn.

Step 2: Add the potatoes and bake

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Add the potatoes and onion to the sauce; transfer to a greased 2-quart baking dish. Cover and bake for one hour.

Step 3: Uncover and continue baking

Uncover and bake the potatoes for another 30 to 40 minutes or until the potatoes are tender. If desired, top with additional pepper.

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Recipe Variations

• Add some crunch: After the first hour of baking, top the uncovered potatoes au gratin with bread crumbs before the final baking period.
• Add fresh herbs: Stir in a total of 2 teaspoons of fresh herbs into the cheese sauce. Use thyme leaves, chopped rosemary, parsley or sage.
• Switch up the potatoes: For a colorful and nutrient-packed substitution, replace half of the Russet potatoes with thinly sliced sweet potatoes for a colorful variation.

How to Store Au Gratin Potatoes

Leftovers can be stored in an airtight container in the refrigerator for up to five days. For best results, reheat leftovers in a 350º oven for about 30 minutes or until heated through.

Can you make au gratin potatoes ahead of time?

Au gratin potatoes are perfect for prepping ahead. You can prep the potatoes up to one day in advance, cover and refrigerate. When ready to bake, remove the baking dish from the refrigerator while the oven preheats. Cook as instructed.

How do you freeze au gratin potatoes?

To freeze, first let the au gratin potatoes cool completely. Then, transfer the potatoes in an airtight freezer-safe container and freeze for up to three months. Thaw overnight in the fridge and then reheat in a 350º oven for 30 to 35 minutes, or until heated through.

Au Gratin Potatoes Tips

Why did my potatoes au gratin curdle?

Curdling can occur when high heat affects the fat in dairy. In this recipe, we thicken the milk with flour to prevent curdling. Starch will also help, so make sure to use a high-starch potato like a russet. If you have leftover potatoes, use them in any of these russet potato recipes.

How do you keep potatoes au gratin from becoming watery?

To keep au gratin potatoes from becoming watery, consider replacing the milk with heavy cream, which has a higher fat content, resulting in a thicker sauce. Make sure to cook the sauce until thickened, so when you add the cheese it’s the right consistency.

Also, use the right potato: Russet potatoes have less water and more starch, making them ideal for au gratin recipes. If your au gratin potatoes are watery while baking, you can add a few shakes of potato flakes, if you have them on hand. They’ll reconstitute in the sauce and act as a thickener.

What goes well with au gratin potatoes?

Just about anything goes well with au gratin potatoes. Lemon thyme chicken is easy and delicious—and bakes at the same temperature as the potatoes. A pork roast is also a classic pairing with au gratin potatoes. Feeling more like a steakhouse dinner? Try a garlic-grilled steak or any of our other steak recipes.