Name: Potatoes Au Gratin
Prep time: 20 min
Cook time: 75 min
Total time: 95 min
Ingredients: 4 large russet potatoes (peeled and thinly sliced using a mandolin or sharp knife); 2 cups heavy cream; 2 ½ cups Gruyère cheese (grated and divided); 1 cup yellow onion (halved and thinly sliced crosswise); 2 tablespoons olive oil; 3 tablespoons unsalted butter; Salt and black pepper (to taste)

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Every time I make Potatoes Au Gratin, I’m reminded why this classic never gets old. The russet potatoes bake up soft and tender, soaking in all that Gruyère cream while the onions add sweetness to every bite. The golden, bubbly top with those crispy edges is pure comfort. This is the kind of side dish people remember long after dinner’s over.

A close-up of a serving spoon lifting creamy Potatoes Au Gratin from a white casserole dish, garnished with chopped parsley. — Potatoes Au Gratin. Photo Credit: Splash of Taste.

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I make this for Thanksgiving, Christmas dinner, Easter brunch, and potlucks when I need an impressive side dish that feeds a crowd. It’s easy to make ahead and bake right before serving, which takes so much stress off holiday cooking. It’s always the first dish to disappear, and people always ask for the recipe. Store leftovers in the fridge for up to 4 days.

Ingredients You’ll Need

You’ll need all the ingredients shown in the photograph below.

A top view of labeled ingredients for Potatoes Au Gratin, including russet potatoes, Gruyère cheese, yellow onion, heavy cream, butter, olive oil, pepper, salt, and parsley. — Potatoes Au Gratin Ingredients. Photo Credit: Splash of Taste.

How to Make Potatoes Au Gratin with Step-By-Step Instructions

Scroll down for the full recipe card containing a full printable recipe and measurements in both US customary and metric units.

I think you’ll find these perfectly creamy potatoes au gratin easier to make than you expect, and the results are absolutely worth it.

Prep the Baking Dish

Preheat your oven to 350°F and generously butter a ceramic baking dish. The butter prevents sticking and adds extra richness to the bottom layer of potatoes.

Caramelize the Onions

Heat and melt butter with a splash of olive oil in a nonstick skillet over medium-low heat. I use unsalted butter for better control over saltiness.

Add the sliced onions and cook for about 10 minutes, stirring occasionally, until they’re soft and lightly golden. The low heat brings out their natural sweetness without burning them.

Mix the Cream Sauce

In a large mixing bowl, whisk together the heavy cream, 2 cups of the grated cheese (I use Gruyère), 1 teaspoon salt, and ½ teaspoon black pepper. Whole milk is a lighter alternative to heavy cream that works in a pinch.

You could use sharp cheddar cheese instead of Gruyère if you’d like a sharper, tangier flavor that’s just as delicious. Stir in the cooked onions so they’re evenly distributed throughout the cream and cheese mixture.

You can also add 2 to 3 cloves of minced garlic here for a savory kick, or some fresh thyme leaves for an earthy, aromatic flavor. Don’t forget to taste the cream mixture and add more salt if needed at this stage, since the potatoes will absorb a lot of seasoning.

Layer the Potatoes

Arrange the thinly sliced potatoes evenly in your prepared casserole dish. You can use Yukon Gold potatoes or red potatoes in place of russet, if that’s what you have.

A mandoline slicer makes quick work of getting uniform slices that cook evenly. If you want to go manual, a sharp knife is perfectly fine. Pour the creamy white sauce over them, making sure every slice gets coated.

Add the Cheese Topping

Sprinkle the remaining ½ cup Gruyère cheese evenly over the top layer. This creates that irresistible golden, crispy crust while the potatoes bake.

For extra nuttiness and a crispier, more golden crust, feel free to add 2 tablespoons of grated Parmesan cheese.

Bake Until Golden

Bake uncovered for 1 to 1¼ hours, or until the potatoes are fork-tender, the cheese is bubbly and completely melted, and the top is golden brown.

Check the potatoes at 1 hour by inserting a sharp knife into the center. If it slides through easily, they’re done, but thicker slices may need the full 1¼ hours of cook time.

A baked dish of Potatoes Au Gratin sits on a wooden board, surrounded by parsley, green onions, a pepper grinder, and a small bowl of salt. — Bake for 60–75 minutes, checking at the one-hour mark to ensure a knife slides easily through the center.

Rest and Serve

Let it rest for 10 minutes before serving so the cheesy cream sauce thickens slightly and doesn’t run all over the plate, especially if potatoes have released any excess liquid while they’re baking.

Once nicely set, serve au gratin potatoes warm and enjoy!

Cover the dish tightly with aluminum foil and wrap it in a thick kitchen towel to keep it warm during transport. You can also place it in an insulated casserole carrier to maintain the temperature for up to 2 hours.

Potatoes Au Gratin

I love making Potatoes Au Gratin for holiday dinners and potlucks when I need a side dish that looks impressive but doesn't stress me out. Layers of thinly sliced russet potatoes get soaked in rich Gruyère cream with caramelized onions mixed throughout for extra flavor. The dish bakes until golden and bubbly while the potatoes become melt-in-your-mouth tender. I serve it for Thanksgiving, Christmas, Easter, and Sunday suppers because it's make-ahead friendly and always disappears fast.

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Prep Time: 20

Cook Time: 1 15

Total Time: 1 35

Course: Dinner, Side Dish

Cuisine: French

Servings:

Calories: 532kcal

Equipment

Ingredients

4 large russet potatoes peeled and thinly sliced using a mandolin or sharp knife
2 cups heavy cream
2 ½ cups Gruyère cheese grated and divided
1 cup yellow onion halved and thinly sliced crosswise
2 tablespoons olive oil
3 tablespoons unsalted butter
Salt and black pepper to taste

Metric – US Customary

Video

Instructions

Preheat the oven to 350°F (180°C). Generously butter a 10 × 15 × 2-inch baking dish and set aside.
Heat the butter with a splash of olive oil in a skillet over medium-low heat. Add the onions and cook for about 10 minutes, stirring occasionally, until soft and lightly golden. Remove from heat.
1 cup yellow onion, 2 tablespoons olive oil, 3 tablespoons unsalted butter
In a large bowl, whisk together the heavy cream, 2 cups of the grated Gruyère, 1 teaspoon salt, and ½ teaspoon black pepper. Stir in the cooked onions.
2 cups heavy cream, 2 ½ cups Gruyère cheese, Salt and black pepper
Arrange the sliced potatoes evenly in the prepared baking dish. Pour the cream mixture over the potatoes, making sure they are well coated.
4 large russet potatoes
Sprinkle the remaining ½ cup Gruyère cheese evenly over the top.
Bake uncovered for 1 to 1¼ hours, or until the potatoes are tender, the sauce is bubbly, and the top is golden brown.
Let rest for 10 minutes before serving to allow the sauce to set.

Notes

I always share my best tips to help you get perfect results every time.

Don’t skip the butter on the dish: Generously buttering the baking dish prevents sticking and adds extra richness to the bottom layer that you’ll appreciate when serving.

Cook the onions low and slow: Keep the heat at medium-low for the full 10 minutes so the onions caramelize and sweeten without burning or turning bitter.

Slice the potatoes uniformly: Use a mandolin to get thin, even slices so they cook at the same rate and create tender layers throughout the dish.

Let the cream mixture coat every slice: Pour slowly and use a spoon to lift and shift the potatoes slightly so the cream gets between all the layers.

Rest before serving: Let the dish sit for 10 minutes after baking so the sauce thickens and sets slightly, making it easier to serve without the cream running everywhere.

Store properly: Let the baked dish cool completely at room temp for about 1 hour before covering or wrapping to prevent condensation or a soggy top. Chill for 3 to 4 days or freeze for up to 3 months, then thaw overnight in the fridge and warm in the oven or microwave.

Nutrition

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How to Store Leftovers

Let leftover potatoes au gratin cool completely, then cover the baking dish tightly with plastic wrap or silicone casserole lid, or transfer individual servings to airtight containers.

They’ll stay fresh in the fridge for 3 to 4 days. Reheat in a 350°F oven for 15 to 20 minutes until heated through, or microwave individual portions for 1 to 2 minutes.

For longer storage, let them cool completely and wrap the dish tightly in plastic wrap, then aluminum foil, or freeze portions in freezer-safe containers for up to 3 months. Thaw overnight in the fridge before reheating.

What to Serve With Potatoes Au Gratin

They’re the perfect side dish for vegetarian mains like mushroom Wellington, stuffed portobello mushrooms, or lentil loaf. The creamy, rich potatoes pair beautifully with hearty vegetable-based entrées and make holiday dinners feel complete and hearty.

Serve them alongside a fresh green salad with lemon vinaigrette or roasted vegetables like Brussels sprouts and green beans to balance the richness. For brunch, they’re excellent with quiche or frittata. Add crusty bread for soaking up any extra cream sauce, and you’ve got an impressive feast everyone will love.

More Easy Recipes for You to Try at Home

If you love potatoes, try these other delicious potato recipes for any occasion.

Potatoes Au Gratin

Ingredients You’ll Need