Cheesy Potato Casserole Recipe with a Creamy Cheese Sauce

This cheesy potato casserole recipe makes tender, evenly sliced potatoes in a creamy cheese sauce with a browned, bubbling top. It serves eight as a side dish and bakes in a 9×13-inch pan.

Use raw 1/8-inch potato slices rather than precooking them. The thin, even cuts cook directly in the sauce, while the sauce thickens enough to coat every slice before baking.

Cheesy Potato Casserole Recipe Essentials for a 9×13-Inch Pan

Gather the ingredients before slicing the potatoes. Freshly shredded cheese melts more smoothly than pre-shredded cheese, which can contain starches that make the sauce grainy.

2½ pounds Yukon Gold potatoes, peeled or scrubbed and sliced 1/8 inch thick
5 tablespoons unsalted butter
1/3 cup all-purpose flour
2½ cups whole milk
1 cup heavy cream
1¼ teaspoons kosher salt, plus more for the potatoes if needed
½ teaspoon black pepper
½ teaspoon garlic powder
¼ teaspoon dry mustard
2 cups shredded sharp cheddar cheese
1 cup shredded Gruyère or Monterey Jack cheese

Coat a 9×13-inch baking dish with butter or nonstick spray. Heat the oven to 375°F. Set aside ½ cup of the combined shredded cheese for the topping. The remaining 2½ cups will go into the sauce.

Yukon Gold potatoes provide a naturally creamy texture and hold their shape well. Russet potatoes also work, but they soften more quickly and may create a slightly starchier sauce.

Prepare 2½ Pounds of Potatoes for a Cheesy Potato Bake

Slice the potatoes into uniform 1/8-inch rounds. A mandoline makes consistent cuts, but a sharp chef’s knife works when you check the thickness as you go. Even slices matter more than speed because thick pieces stay firm while thin pieces overcook.

Peel the potatoes for a smooth, classic casserole, or leave the skins on after scrubbing them well.
Slice each potato crosswise into 1/8-inch rounds.
Do not boil or par-cook the slices. They will cook fully in the covered casserole.
Do not soak or rinse the sliced potatoes. Their surface starch helps the cheese sauce cling and thicken.
Arrange the slices in loose, overlapping layers while the sauce is prepared. Avoid pressing them into a dense, compact stack.

If the potatoes must wait more than a few minutes, cover them with a clean, slightly damp towel. Do not leave them submerged in water, since excess moisture can dilute the sauce and delay browning.

Make Creamy Cheesy Potatoes with a Thick Sauce

The sauce should be thick enough to coat the back of a spoon before it goes into the dish. It should still pour easily; a sauce that is stiff in the saucepan will become too dense after the cheese melts and the casserole bakes.

Melt the butter in a medium saucepan over medium heat. Add the flour and whisk constantly for about 1 minute, until the mixture is smooth and lightly foamy.
Slowly pour in the milk and heavy cream while whisking. Add the salt, pepper, garlic powder, and dry mustard.
Cook for 5 to 7 minutes, whisking often, until the sauce visibly thickens. A spoon dragged across the bottom should leave a clear trail for a moment.
Remove the saucepan from the heat. Add the 2½ cups of cheese a handful at a time, whisking until each addition melts before adding more.
Taste the sauce and adjust the seasoning. It should taste slightly bold because the potatoes will mellow the salt and cheese flavor.

Keep the sauce below a simmer after adding the cheese. Boiling can cause the fat to separate, producing a greasy or grainy texture. If the sauce becomes too thick, whisk in 1 or 2 tablespoons of milk before assembling.

Pour about one-third of the cheese sauce into the prepared pan. Add one-third of the potato slices, overlapping them slightly. Repeat the layers, finishing with the remaining sauce. Gently press the potatoes down with a spatula so the sauce reaches the spaces between the slices.

Bake the Creamy Potato Casserole at 375°F for 60–75 Minutes

Spread the reserved ½ cup of cheese evenly over the surface. Cover the dish tightly with aluminum foil, keeping the foil from touching the cheese if possible. The cover traps steam so the raw potato slices cook before the top becomes too dark.

Bake the covered casserole at 375°F for 45 minutes.
Remove the foil and continue baking for 15 to 30 minutes, until the cheese is deeply golden and the sauce bubbles around the edges.
Begin checking at the 60-minute mark. Insert a thin knife or fork into the center, where the potatoes take longest to cook.
Continue baking until the utensil slides through the potatoes with little resistance. This fork-tender cue matters more than the color of the top.
If the top browns before the center is tender, loosely cover the dish again and bake for another 10 to 15 minutes.

Total baking time is usually 60 to 75 minutes, depending on the potato variety, slice accuracy, and how cold the ingredients were. A firm center, watery-looking sauce, or resistance from the fork means the casserole needs more time.

Let the casserole rest uncovered for 10 to 15 minutes before serving. The sauce will thicken as it settles, making the creamy cheesy potatoes easier to spoon without losing their browned cheese crust.