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Jump to RecipeThese potatoes au gratin are creamy, cheesy and completely irresistible. Thin slices of Yukon Gold potatoes are layered with a silky garlic and thyme cream sauce and plenty of Gruyère, sharp cheddar and Parmesan, then baked until the potatoes are fork tender and the top is golden and bubbling. It is the kind of side dish that disappears first at every holiday dinner.
This classic French inspired casserole is elegant enough for Thanksgiving, Christmas and Easter, yet simple enough for a Sunday roast. You can assemble it ahead, which makes entertaining much easier. Serve it with roast chicken, ham, steak or a hearty main like my easy homemade Bolognese. For another cheesy side, try my slow cooker mac and cheese.
Why You Will Love These Potatoes au Gratin
- Creamy and cheesy. A rich garlic cream sauce and three cheeses in every layer.
- Golden, crispy top. Baked uncovered at the end for a bubbly crust.
- Holiday ready. Make ahead friendly and feeds a crowd.
- Foolproof sauce. A simple roux keeps the sauce smooth and prevents curdling.
- Versatile. Pairs with almost any main dish.
Au Gratin vs Scalloped Potatoes
These two dishes look similar, but there is one key difference: cheese. Traditional scalloped potatoes are thinly sliced potatoes baked in a creamy sauce, usually without cheese, and sometimes with breadcrumbs on top. Potatoes au gratin always include cheese, both between the layers and on top, which creates a richer dish with a golden, crispy crust.
The word gratin comes from the French word for the browned crust that forms on top of a baked dish. In many American homes the names are used interchangeably, but if you want that cheesy, bubbly topping, you want au gratin.
Ingredients You Will Need
Exact amounts are in the recipe card below.
- Yukon Gold potatoes: they hold their shape and turn buttery and creamy. Russets also work and are a little fluffier.
- Butter and all purpose flour: make a roux that thickens the sauce.
- Onion and garlic: add savory depth.
- Whole milk and heavy cream: together they create a rich but not overly heavy sauce.
- Gruyère cheese: nutty, melty and classic in gratins.
- Sharp cheddar: adds tang and color.
- Parmesan: for a salty, crispy top.
- Fresh thyme, salt, pepper and a pinch of nutmeg: the classic seasonings for a cream sauce.
How to Make Potatoes au Gratin
1. Prep the oven and potatoes
Preheat the oven to 375°F and butter a 9×13 baking dish. Peel the potatoes and slice them into even 1/8 inch rounds. A mandoline is the fastest way to get uniform slices, or use a sharp chef knife. Keep the slices in a bowl of cold water until you are ready so they do not brown, then drain and pat dry.
2. Make the cream sauce
Melt the butter in a saucepan over medium heat. Add the onion and cook for 3 to 4 minutes until soft, then add the garlic for 30 seconds. Sprinkle in the flour and whisk for 1 minute. Slowly whisk in the milk and cream, then add the thyme, salt, pepper and nutmeg. Simmer, whisking often, for 3 to 5 minutes until thickened. Remove from the heat and stir in half of the Gruyère and cheddar until melted.
3. Layer the potatoes
Arrange a third of the potato slices in overlapping rows in the baking dish. Pour a third of the sauce over the top and spread it with a spatula. Repeat twice more, making sure the top layer of potatoes is well covered with sauce. Sprinkle the remaining Gruyère, cheddar and the Parmesan evenly over the top.
4. Bake covered, then uncovered
Cover the dish tightly with foil and bake for 45 minutes. Remove the foil and bake for another 25 to 35 minutes, until the potatoes are completely tender when pierced with a knife and the top is deep golden brown and bubbly. Place a sheet pan on the rack below to catch any drips.
5. Rest before serving
Let the potatoes rest for 15 minutes before serving. This gives the sauce time to thicken and set, so each slice holds its layers. Garnish with fresh thyme leaves.
Tips for Perfect Potatoes au Gratin
- Slice evenly. Uniform slices cook at the same rate, so there are no crunchy bits.
- Do not rinse off all the starch. A quick soak is fine, but the starch helps thicken the sauce.
- Warm the milk. Warm dairy blends into the roux more smoothly.
- Cover first. Baking under foil steams the potatoes until tender before the top browns.
- Let it rest. Cutting too soon makes the sauce runny.
Best Potatoes for Au Gratin
Yukon Gold potatoes are my favorite for au gratin. They have a medium starch content, a naturally buttery flavor and a thin skin, and they hold their shape beautifully while turning creamy in the sauce. Russet potatoes have more starch, so they create a softer, fluffier texture and help thicken the sauce, but their slices can break apart more easily. Red potatoes are waxy and stay very firm, which some people love, though they do not absorb the sauce as well. Whichever you choose, pick potatoes that are firm with no green spots or sprouts.
Easy Variations
- Bacon and chive: sprinkle crispy bacon and chives between the layers.
- Ham and cheese: add diced ham for a hearty main dish.
- Different cheeses: try fontina, Havarti, smoked gouda or white cheddar.
- Caramelized onion: layer in slow cooked onions for sweetness.
- Sweet potato gratin: swap in half sweet potatoes for color and flavor.
- Crispy topping: scatter buttered panko over the cheese before the final bake.
How to Slice Potatoes Evenly
Even slices are the single most important step for a perfect gratin. When every slice is the same thickness, every layer cooks at the same rate, so you never bite into a crunchy potato next to a mushy one. A mandoline slicer set to 1/8 inch is the fastest and most consistent tool, and it turns a few pounds of potatoes into neat rounds in minutes. Always use the hand guard, since the blade is extremely sharp. If you do not have a mandoline, a food processor fitted with a thin slicing disc also works well.
With a knife, cut a thin slice off one side of each potato so it sits flat and stable on the board, then slice slowly and steadily. Aim for slices about as thick as two stacked coins. Store the slices in cold water while you work, but drain and pat them dry before layering so the sauce is not watered down.
Tips for Serving a Holiday Crowd
This recipe serves about eight as a side, but it is easy to double for a big gathering. Use two 9×13 dishes rather than one very deep dish, since a deep gratin takes much longer to cook through in the center. Assemble both the day before and refrigerate. On the day, bake them while your roast rests, rotating the dishes between racks halfway through.
Au gratin potatoes hold their heat well, so they can sit covered with foil for 20 to 30 minutes while you finish the rest of the meal. Cut them into squares with a sharp spatula for neat portions, and garnish with fresh thyme or chives for a festive look.
What to Serve With Potatoes au Gratin
Potatoes au gratin pair beautifully with roast chicken, glazed ham, prime rib, pork tenderloin or steak. For a lighter plate, add roasted green beans, asparagus, Brussels sprouts or a crisp salad. They are also delicious next to my oven baked chicken breast or chicken pot roast.
Make Ahead, Storage and Reheating
- Make ahead: assemble the gratin, cover and refrigerate for up to 24 hours. Let it sit at room temperature for 30 minutes and add 10 to 15 minutes to the covered baking time.
- Bake ahead: bake fully, cool, refrigerate and reheat covered at 350°F for 25 to 30 minutes.
- Leftovers: store in glass containers for up to 4 days.
- Freezing: baked gratin can be frozen for up to 2 months, though the sauce may become slightly grainy.
Common Mistakes to Avoid
- Uneven slices. Thick slices stay hard while thin ones turn mushy.
- Skipping the roux. Cream alone can curdle and turn greasy in the oven.
- Not enough sauce. Potatoes on top that are not covered can dry out.
- Serving immediately. A 15 minute rest makes all the difference.
Frequently Asked Questions
Can I use Yukon Gold or Russet potatoes interchangeably?
Yes. Yukon Golds are creamier and hold their shape, while Russets are starchier and softer.
Why are my potatoes still hard?
The slices may be too thick or the dish needs more time covered. Bake until a knife slides through easily.
Why did my sauce curdle?
Very high heat or too little starch can cause separation. The flour roux in this recipe helps prevent it.
Can I make potatoes au gratin ahead?
Yes. Assemble up to a day ahead and bake before serving, or bake ahead and reheat.
Do I need to peel the potatoes?
Peeling gives a classic smooth texture, but thin skinned Yukon Golds can be left unpeeled.
Can I halve the recipe?
Yes. Use an 8×8 baking dish and reduce the baking time slightly.
Final Thoughts
Potatoes au gratin are the ultimate comfort side dish, with tender layers of potato, a creamy garlic sauce and a bubbly, golden cheese crust. They are easy to make ahead, perfect for holidays and loved by everyone at the table. Once you make them from scratch, you will never go back to the boxed version.
Nutrition Per Serving
| Nutrient | Amount |
|---|---|
| Calories | 410 kcal |
| Protein | 15 g |
| Carbohydrates | 32 g |
| Fat | 25 g |
| Saturated Fat | 15 g |
| Fiber | 3 g |
| Sugar | 4 g |
| Sodium | 620 mg |
Nutrition values are estimates calculated from standard ingredient data and will vary with the brands and exact amounts you use.
Potatoes au Gratin
Ingredients
Method
- Preheat the oven to 375°F and butter a 9×13 baking dish. Slice the potatoes 1/8 inch thick.
- Melt the butter, cook the onion 3 to 4 minutes, add the garlic, then whisk in the flour for 1 minute.
- Slowly whisk in the milk and cream, add the thyme, salt, pepper and nutmeg and simmer 3 to 5 minutes. Stir in half the Gruyère and cheddar.
- Layer the potatoes and sauce in thirds, then top with the remaining cheeses and Parmesan.
- Cover and bake 45 minutes, then uncover and bake 25 to 35 minutes until tender and golden.
- Rest 15 minutes before serving.
