Potatoes Au Gratin

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Potatoes au gratin is layers of thinly sliced spuds together with a creamy sauce and melted cheese. A rich bechamel sauce that is thickened with a roux is spread between the potatoes which creates a luxurious texture. This casserole recipe is baked until hot, bubbly, and the cheese is golden brown. It’s the potato version of macaroni and cheese that disappears fast the moment it’s served!

Spoon lifting a serving of potatoes au gratin from a casserole dish

Cheesy potatoes au gratin is a classic side dish that’s easy to prepare and is always a crowd-pleaser. Except if the cream curdles or the potatoes aren’t fork-tender after baking, but with the right guidance, I’m going to show you how these common problems can be easily avoided.

This recipe uses multiple layers of very thinly sliced Yukon gold potatoes topped with a roux-based sauce to stabilize the milk in the dish. Aged sharp cheddar and buttery gruyere cheese mix together in the sauce and get sprinkled on the potatoes. It’s a comforting dish that can be prepared ahead of time and enjoyed later.

two types of cheeses being whisked into a roux-based pan sauce

What’s the difference between scalloped potatoes and Au Gratin Potatoes?

Scalloped potatoes are traditionally cut into thicker rounds, about ¼-inch, layered and baked in a casserole dish. Cream, milk (or both) are added, along with some aromatics like garlic, onions, and herbs. Au gratin potatoes, on the other hand, are thinner, about ⅛-inch thick pieces and cheese is added to the recipe. You might also sometimes see breadcrumbs sprinkled on top for extra crunch. The culinary terms are often used interchangeably which causes a bit of confusion.

How to make Au Gratin sauce

The basic technique used to create a milk sauce is using a thickening agent, like a roux. This recipe uses equal parts by volume of butter and flour which cooks into a paste, then gradually incorporating milk while simmering until the thickness can nicely coat a spoon.

The result is a bechamel with cheese whisked in. This is technique is also used in macaroni and cheese, but we’re using potatoes instead of pasta. If made correctly, the sauce should spread easily between the potato layers instead of pooling at the bottom of the baking dish.

spatula spreading a layer of cream sauce over thinly sliced potatoes in a casserole dish

How to prevent the sauce from curdling

If you only add milk to the potatoes, the proteins are at risk for curdling over time. Once the protein hits a temperature of 180ºF and above they begin clumping together. That’s why recipes often use milk AND cream because the increased amount of fat helps reduce curdling since there’s less protein. Considering the potatoes are cooked at 400ºF for nearly an hour to tenderize, it’s best to build in a little safety cushion with a roux. The creamy texture added to the sauce is just a tasty bonus!

The best potatoes to use for Au Gratin

Choose a medium-sized waxy type of potato like Yukon gold or gold for au gratin. Once cooked the flesh has a nice buttery texture, but it holds its shape well when scooping out each serving. Russets are my second choice because, with their delicate texture, they tend to absorb the sauce and become too creamy. I prefer to use Russet potatoes for mashed potatoes instead.

grated pieces of gruyere and sharp cheddar cheese sprinkled on top of uncooked potatoes au gratin casserole

Cheese selection

The best combination of cheese to use for the au gratin potatoes is gruyere and sharp cheddar. Gruyere is a medium-hard cheese that has a nutty taste and hint of sweetness. It has excellent melting properties, and I always use it when making French onion soup. Sharp cheddar has a stronger aged flavor and a semi-hard texture. Together they melt effortlessly in the bechamel sauce and create a nice gooey, browned crust on top of the potatoes.

Key tips for making potatoes Au Gratin

  • Peel and slice the potatoes into ⅛-inch thick pieces for even cooking. I recommend using a mandoline.
  • Overlap half the potatoes to create a base, spread the sauce, cheese, and repeat.
  • Infuse more flavor by adding gruyere and cheddar cheese into the sauce, and sprinkling extra between the layers.
  • Cover the baking dish with foil to help gently cook the potatoes.
  • Finish cooking the potatoes uncovered to create a melty, golden cheese crust.

Use a large serving spoon to dig into the layers of the cheesy potatoes. Each bite melts in your mouth, and the flavors of the garlic and nutmeg infuse into each piece. This side dish can be assembled ahead of time and then baked right before serving. My family also enjoyed leftovers of the potatoes and it still tasted delicious warmed up!

potatoes au gratin hot and fresh from the oven

More side dish recipes

Starches help to stabilize the cream sauce

The natural starches in flour helps to stabilize the milk emulsion in the sauce, preventing the separation of the oils and fat. When the starches are heated, they’re able to hold onto some of the water in the milk, swell, and create a viscous mixture. By incorporating a roux into a dairy-based sauce will thicken and stay creamy once baked in the oven.

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Potatoes Au Gratin

Potatoes au gratin is a casserole recipe with layers of thinly sliced Yukon gold spuds and a cream sauce that includes melted cheese.
Pin Print Review
4.22 from 61 votes
Prep Time20 mins
Cook Time1 hr
Total Time1 hr 20 mins
Servings 8 servings
Course Side
Cuisine French

Ingredients

  • ¼ cup unsalted butter
  • 1 tablespoon minced garlic
  • ½ cup finely chopped yellow onion
  • ¼ cup all-purpose flour
  • 2 cups whole milk
  • ¾ teaspoon kosher salt
  • ½ teaspoon black pepper
  • teaspoon nutmeg
  • 2 pounds yukon gold potatoes, peeled and cut into ⅛-inch thick slices
  • 1 cup shredded gruyere cheese
  • 1 cup shredded sharp cheddar cheese
  • 2 teaspoon chopped chives

Instructions 

  • Set the oven rack to the middle position and preheat to 400ºF.
  • Melt butter in a large skillet over medium-low heat. Add garlic and onions, saute until fragrant, 2 minutes.
  • Add flour, whisk to combine, stir and cook for 2 minutes.
  • Gradually whisk in milk and cook until thickened over medium heat, 2 to 3 minutes.
  • Turn off heat and whisk in salt, pepper, nutmeg, ½ cup gruyere, and ½ cup sharp cheddar cheese.
  • Grease the bottom and sides of an 8-inch square casserole dish.
  • Layer half of the potatoes, in overlapping rows in the dish. Spread half of the cheese sauce over the potatoes. Sprinkle ¼ cup gruyere and ¼ cup cheddar over the sauce.
  • Layer the remaining potatoes, followed by cheese sauce, and sprinkle with the remaining gruyere and cheddar cheese.
  • Cover with foil and place on a baking sheet. Bake for 30 minutes, remove the foil and bake until potatoes are tender and cheese is browned and bubbly, 20 to 25 minutes.
  • Garnish potatoes with chives.

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Nutrition Facts
Potatoes Au Gratin
Amount Per Serving
Calories 168 Calories from Fat 63
% Daily Value*
Fat 7g11%
Saturated Fat 4g20%
Cholesterol 21mg7%
Sodium 256mg11%
Potassium 548mg16%
Carbohydrates 20g7%
Fiber 2g8%
Sugar 3g3%
Protein 5g10%
Vitamin A 275IU6%
Vitamin C 13mg16%
Calcium 105mg11%
Iron 3.9mg22%
* Percent Daily Values are based on a 2000 calorie diet.

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Jessica Gavin

I'm a culinary school graduate, cookbook author, and a mom who loves croissants! My passion is creating recipes and sharing the science behind cooking to help you gain confidence in the kitchen.

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30 Comments Leave a comment or review

  1. DawneSN says

    The recipe looked excellent, especially because you include nutmeg. I made it yesterday ahead of time, put in in the fridge, about 2 hours before dinner baked it beginning at 350 then moved it up to 400 for the last hour with foil on top until the last half hour. I liked that discoloration was not much of a problem as the sauce covered the potatoes well.

    I changed the recipe a bit because I didn’t have Swiss cheese, sadly, so used a merlot cheddar and a well aged white cheddar. I also doubled the onions and could have doubled them again. I thought the dish was bland. I’d make it again, but I’d add more salt and pepper and more nutmeg (mine was not super fresh).

    Our guest loved it and my husband and I added more salt and pepper.

  2. Alysa says

    Do not make this ahead of time and refrigerate overnight. The potatoes will turn brown. Trust me, I did this and they looked terrible.

    • Jessica Gavin says

      Hi Alysa! What part did you make ahead? Was it the entire recipe, or did you just slice the potatoes? Sliced potatoes will turn brown when exposed to air if not submerged in water, or cooked within a few hours (or less!).

  3. JB says

    Has anyone made this recipe the day before and just popped it in the over before dinner? If so how did it turn out..also..if cladding cream do I just substitute for milk or add to the milk?

    • Jessica Gavin says

      Hi There! I think you can assemble everything and then bake with the unmelted cheese before serving, just test to make sure the potatoes are warmed through since it will be refrigerated. What is cladding cream?

      • JB says

        Sorry not cladding …I meant using cream…if I’m using cream so I substitute one for one with milk or add cream in addition to the milk

  4. Ryan Haley says

    This method is perfect, I’ve been using it for years and it’s so consistent! I’m wondering if you’ve ever assembled it the night before baking? I’m concerned that the potatoes might oxidize and leave me with grey au gratin? 😳

    • Jessica Gavin says

      Yukon gold potatoes don’t oxidize are severe as russets. As long as you cover it in the sauce, cheese, and tightly cover in foil in the refrigerator you can assemble it the night before.

  5. Kathy E. says

    This was a fantastic side dish for our Christmas dinner! It went perfectly with our ham and other sides. I used fat-free half and half mixed with skim milk and the sauce was still thick and so rich. It was the only dish that was completely emptied! Thank you for a winner!

  6. Jen says

    In the part before the recipe you say to use milk AND cream so the sauce does curdle but the recipe has no mention of cream. Would you add cream or sub half of the amount of milk for cream?

    • Jessica Gavin says

      Hi Hen- FOr this recipe we use a flour-based roux to help stabilize the milk base. The starches help stabilize the emulsion. I was just comparing why for other recipes they might use a combo of milk and cream if you’re not using flour. You don’t have to add additional cream. Sorry for the confusion!

  7. Lori says

    I made this recipe yesterday and it was a HUGE hit in my house. Very flavorful and creamy. Thanks very much!

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