Delicious au gratin potatoes recipe that’s easy to make during the holidays. It’s the perfect cheesy potato side dish that complements any meal.
Table of Contents
- How to make au gratin sauce
- How to prevent the sauce from curdling
- Cheese selection
- The best potatoes to use for au gratin
- Assemble and bake
- Make ahead
- What’s the difference between scalloped potatoes and au gratin potatoes?
- Potatoes Au Gratin Recipe
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 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.
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. You can use heavy cream for an even richer consistency, but the roux makes the sauce velvety enough.
The result is a bechamel with cheese whisked in. This 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.
How to prevent the sauce from curdling
If you only add milk to the potatoes, the proteins are at risk of curdling over time. Once the protein hits a temperature of 180ºF (82ºC) and above, they begin clumping together. That’s why recipes often use milk and cream because the increased fat helps reduce curdling since there’s less protein.
Considering the potatoes are cooked at 400ºF (204ºC) for nearly an hour to tenderize, it’s best to build a little safety cushion with a roux. The creamy texture added to the sauce is just a tasty bonus!
The best cheese combination for the au gratin potatoes is gruyere and sharp cheddar cheese. Gruyere is a medium-hard cheese with a nutty taste and a 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.
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 their delicate texture tends to absorb the sauce and become too creamy. I prefer to use Russet potatoes for mashed potatoes instead.
Assemble and bake
In a greased 8-inch square baking dish, layer half over the potatoes, overlapping them. Spread half of the cheese sauce and shredded cheese. Repeat the layering once more time with the remaining ingredients. Cover the dish with foil and bake in a preheated oven at 400ºF (200ºC). This traps the heat to steam and softens the spuds. After 30 minutes, remove the foil so that the cheese layer browns. Cook until the potatoes are tender, about 20 to 25 minutes.
This side dish can be assembled two days ahead, covered, and refrigerated until ready to bake. Bake time may need to be slightly increased as the pan and ingredients will be cold. My family also enjoyed leftovers. It still tastes delicious when reheated.
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), and aromatics like garlic, onions, and herbs are added. On the other hand, Au gratin has thinly sliced potatoes, ⅛-inch thick potato slices, and cheese 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.
Serve this with
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 can hold onto some of the water in the milk, swell, and create a viscous mixture. A roux in a dairy-based sauce will thicken and stay creamy once baked in the oven.
Potatoes Au Gratin
- 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
- ⅛ teaspoon nutmeg
- 2 pounds yukon gold potatoes, peeled and cut into ⅛" thick slices
- 1 cup shredded gruyere cheese
- 1 cup shredded sharp cheddar cheese
- 2 teaspoon chopped chives
- Preheat the Oven – Set the oven rack to the middle position. Heat to 400ºF (200ºC).
- Make the Cream – Melt butter in a large skillet over medium-low heat. Add garlic and onions, and 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 the heat and whisk in salt, pepper, and nutmeg.
- Add the Cheeses – Add ½ cup gruyere and ½ cup sharp cheddar cheese, and stir to combine.
- Assemble the Casserole – 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.
- Bake – Cover with foil and place on a baking sheet. Bake for 30 minutes. Remove the foil and continue baking until the potatoes are tender and the cheese is browned and bubbly, 20 to 25 minutes.
- To Serve – Transfer the casserole to cool on a wire rack for 10 to 15 minutes before serving. Garnish potatoes with chives.
- Make Ahead: Assemble, cover, and refrigerate for 2 days before baking. More baking time may be needed as the ingredients and pan will be cold.
- Storing: Store in an airtight container in the refrigerator for up to 5 days. Freeze for up to 1 month.
- Reheating: Cover and reheat a small portion in the microwave on a high setting in 15 to 30-second increments until hot. Alternatively, cover and reheat in the oven at 350ºF (177ºC) until hot.
Percent Daily Values are based on a 2000-calorie diet. All nutritional information is based on estimated third-party calculations. Each recipe and nutritional value will vary depending on the brands you use, measuring methods, and portion sizes per household.
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