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When the foil comes off, the top is still pale and the potatoes are covered in a creamy sauce. The uncovered bake is what turns that surface golden while the potatoes finish softening at the center. These au gratin potatoes are layered in a 9×13-inch dish, so each slice gets sauce between the layers instead of relying on a thick blanket on top.

I use russet potatoes for their tender, starchy texture and make the cheddar sauce on the stovetop before it goes into the dish. The sauce should coat the back of a spoon, not pour like milk; that gives it enough body to cling to the potatoes as they bake. A little rest after baking helps the layers settle, with a browned cheddar top and creamy potatoes underneath.

Why the Cheddar Goes Into the Sauce Off the Heat

Cheddar has plenty of flavor, but it can turn grainy if it gets too hot while melting. The sauce needs to be hot enough to melt the shreds, not bubbling on the burner. Taking the saucepan off the heat before stirring in the cheese gives it a gentler landing and helps keep the sauce smooth.

The flour and butter do a different job: they give the milk and cream enough structure to stay with the potatoes through baking. A sauce that’s too thin can settle at the bottom of the dish, while a properly thickened one coats the spoon and spreads between the layers. Sharp cheddar brings a more pronounced taste through the creamy base, so you don’t have to depend on a heavy layer of cheese on top for flavor. The small amount on the surface can then brown while the sauce underneath stays creamy.

What Russets, Cream, and Cheddar Each Bring to the Dish

• Russet potatoes — Their starch gives the baked layers a soft, tender texture. Choose firm potatoes without green patches; a Yukon Gold swap works, but the slices hold a waxier, less fluffy shape. Peel and slice them shortly before layering.
• Whole milk and heavy cream — Milk keeps the sauce fluid enough to pour, while cream adds richness. If you don’t have both, replace their combined volume with an equal volume of half-and-half; the sauce will be a little less rich. Standard grocery-store dairy is fine here.
• Sharp cheddar — Sharpness stands up to the creamy sauce, and a block shredded at home melts more smoothly than pre-shredded cheese. Monterey Jack can replace it in the same quantity for a milder, softer-tasting result, though it won’t bring the same tang.
• All-purpose flour — This thickens the butter and dairy into a sauce that clings to the potato layers. A measure-for-measure gluten-free flour blend formulated for baking is the most useful swap; the sauce may be a touch less silky. There’s no need for a specialty brand of regular flour.

From a Silky Cheddar Sauce to Tender Potatoes

Prepare the Dish and Slice the Potatoes

Heat the oven to 375°F and grease a 9×13-inch baking dish with softened butter. Peel the russets, then slice them 1/8 inch thick. Take a moment to keep the slices consistent rather than leaving a few noticeably thick pieces. Set the prepared dish nearby so you can layer the potatoes as soon as the sauce is ready.

Build the Cream Sauce

Melt the butter in a medium saucepan over medium heat, whisk in the flour, and cook it for 1 minute. Gradually whisk in the milk and cream; adding them steadily helps the mixture turn smooth instead of lumpy. Whisk in the kosher salt, black pepper, and garlic powder, then cook and stir for about 5 minutes. The sauce is ready when it thickens enough to coat the back of a spoon.

Melt the Cheddar and Layer the Potatoes

Take the saucepan off the heat and stir in 1 1/2 cups of the shredded cheddar until melted. Arrange half the potato slices in the buttered dish and pour half the sauce over them. Add the remaining potatoes and sauce, then scatter the remaining cheddar over the top. Spread the layers across the dish so the sauce isn’t all pooled in one spot.

Bake Until a Knife Slides Through the Center

Cover the dish tightly with foil and bake for 45 to 55 minutes. Uncover and bake for another 20 to 25 minutes, until the top is golden and a knife slides easily into the potatoes at the center. If the top looks ready but the center still resists the knife, the potatoes need more baking time. Let the dish rest for 10 minutes before serving so the layers can settle.

Three Swaps That Change These Au Gratin Potatoes

Questions That Come Up Before Baking Au Gratin Potatoes

Au Gratin Potatoes

Au gratin potatoes bake thinly sliced russet potatoes in a creamy sharp cheddar sauce until tender beneath a golden top. A final uncovered bake gives the cheese a browned finish, while a 10-minute rest helps the layers set.

Print Recipe Pin Recipe

Prep Time 20 minutes mins

Cook Time 1 hour hr 20 minutes mins

Resting 10 minutes mins

Total Time 1 hour hr 50 minutes mins

Servings: 8 servings

Course: Side Dish

Cuisine: American

Calories: 430

Ingredients Equipment Method Notes

Ingredients

  

For the potatoes

• 1 tbsp butter unsalted, softened, for greasing
• 2 lb potatoes russet, peeled and sliced 1/8 inch thick

For the cheese sauce

• 3 tbsp butter unsalted
• 3 tbsp all-purpose flour
• 2 cups whole milk
• 1 cup heavy cream
• 1 tsp kosher salt
• 0.5 tsp black pepper
• 0.25 tsp garlic powder
• 2 cups sharp cheddar cheese shredded and divided

Equipment

• 1 9x13-inch baking dish

Method

 

Prepare the potatoes

1. Heat the oven to 375°F and grease a 9x13-inch baking dish with the softened butter.
2. Peel and slice the potatoes 1/8 inch thick.

Make the cheese sauce and bake

1. Melt the butter in a medium saucepan over medium heat, whisk in the flour, and cook for 1 minute.
2. Gradually whisk in the milk and cream until smooth.
3. Whisk in the salt, pepper, and garlic powder.
4. Cook, stirring, until the sauce thickens enough to coat the back of a spoon, about 5 minutes.
5. Remove the saucepan from the heat and stir in 1 1/2 cups of the cheddar until melted.
6. Arrange half of the potatoes in the baking dish and pour over half of the cheese sauce.
7. Layer in the remaining potatoes and sauce, then sprinkle the remaining 1/2 cup cheddar over the top.
8. Cover the dish tightly with foil and bake for 45 to 55 minutes.
9. Uncover and bake for 20 to 25 minutes, until the top is golden and a knife slides easily into the potatoes at the center.
10. Let the potatoes rest for 10 minutes before serving.

Notes

Slice the potatoes evenly so they cook at the same rate. Refrigerate leftovers for 3 to 4 days; freezing is not recommended because the cream sauce may separate. For a gluten-free swap, use gluten-free all-purpose flour.