Potatoes au gratin is the perfect side dish for Sunday supper or as a make-ahead holiday side dish. Tender layers of potatoes and onions are baked in a rich, creamy, cheesy sauce until hot, bubbly, and golden.
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Holly’s Recipe Highlights
This recipe makes creamy potatoes, similar to scalloped potatoes but loaded with rich cheesy flavor. They are the perfect dish next to a baked ham, roast beef tenderloin or pork tenderloin.
- Flavor: Creamy, cheesy, and comforting with a golden, slightly crispy top that makes every bite irresistible.
- Why it works: A cooked roux thickens the sauce so it coats the potatoes instead of pooling thin at the bottom.
- Recommended Tools: To save time on prep and make even and thin potato and onion slices, use a mandoline or the side of a box grater.
- Time-Saving Tip: For the holidays, I usually put it together ahead of time and then bake it fresh just before serving. It makes life so much easier.
Scalloped Potatoes vs Potatoes au Gratin
So what is the difference between scalloped potatoes and au gratin potatoes? They’re both very similar, containing potatoes (and often onions) baked in a creamy sauce. Au Gratin is defined as covered with breadcrumbs or cheese, scalloped refers to “bake with milk or a sauce”.
In the case of this recipe, the difference is the cheese. That being said, the term scalloped potatoes is still often used if there is cheese within the dish!
Best Potatoes to Use for Potatoes au Gratin
Red-skinned or Yukon Gold potatoes are best for gratin because they hold their shape and don’t need peeling, while starchy russets can turn mushy and are better for mashing.
- Onions: Slice paper-thin so it softens fully and doesn’t stay crunchy.
- Mustard Powder: A small amount enhances the cheese flavor (I also add it to my baked mac and cheese!). Swap in a little Dijon stirred off the heat.
- Cheese: For the best potatoes au gratin, use bold, sharp cheeses like Gruyère or cheddar, with provolone or Swiss as good substitutes.
- Variations: Add flavor with minced garlic, garlic powder, or fresh herbs like thyme or rosemary. You could also include ham or cooked bacon for a heartier casserole.
How to Make Potatoes Au Gratin
- Prep: Thinly slice the potatoes and onions (full recipe below).
- Assemble: Stack the potato slices and onions in the casserole dish.
- Sauce: Cook the cheese sauce in a saucepan, then pour it over the potato and onion slices.
- Bake: Bake until the potatoes are tender and the sauce is bubbly.
PRO TIP: For a quicker version, layer potatoes and onions, cover, and microwave 10 minutes. Add cheese sauce and bake 45–55 minutes as directed. Just as delicious, but a little quicker!
Make-Ahead, Storing, and Reheating
Make up to 24 hours ahead. Keep potatoes covered in sauce, cover tightly, and refrigerate. Bring to room temperature before baking, and add 10–20 minutes to the bake time.
Leftover potatoes au gratin will keep in the refrigerator for up to 4 days. Let it cool completely, then cover tightly with plastic wrap, or transfer to an airtight container before refrigerating.
To freeze, allow it to cool completely and wrap the dish well with both plastic wrap and aluminum foil, or portion it into freezer-safe containers. It will keep for up to 2 months in the freezer.
For best results, thaw overnight in the refrigerator before reheating. Reheat covered in the oven at 350°F until hot throughout (about 20 to 30 minutes), removing the cover near the end to crisp up the top again. Avoid microwaving frozen potatoes, as it can make the sauce grainy and the potatoes watery.
More Holiday Side Dishes
Did you make this Potatoes au Gratin recipe? Leave us a rating and comment below.
Ingredients
- 2½ pounds red potatoes
- 1 medium onion thinly sliced
- 3 tablespoons butter
- 3 tablespoons all-purpose flour
- 1 teaspoon dry mustard powder
- 2 cups milk
- 1 cup shredded cheddar cheese
- ½ cup shredded gruyere cheese
- ¾ teaspoon salt divided
- ½ teaspoon black pepper divided
Instructions
- Preheat oven to 400°F.
- Wash potatoes and slice into ⅛" thin slices. Slice onion as thinly as possible.
- Season the potatoes and onions with ½ teaspoon of salt and ¼ teaspoon of pepper. Toss well to evenly coat. Layer potatoes and onions into little stacks. Place stacks on their side in a greased 2.5QT to 3QT casserole dish.
- In a saucepan, melt butter and flour and cook for 2 to 3 minutes. Add mustard powder, ¼ teaspoon salt, ¼ teaspoon pepper, and milk. Whisk over medium heat until thick and bubbly. Remove from heat and stir in cheeses until melted.
- Pour the cheese sauce over the potatoes, gently separating the stacks to allow the sauce to seep between the layers. Cover with foil (sprayed with cooking spray) and bake for 60 minutes.
- Remove foil and bake an additional 20 to 30 minutes or until lightly browned and potatoes are cooked. Cool 15 minutes before serving.
Video
Notes
- Slice potatoes as thinly as possible.
- Shred your own cheese from a block for the best results. Fresh herbs (such as thyme or rosemary) and garlic can be added to the sauce if desired.
- To reduce baking time, wrap a microwave-safe casserole dish in plastic wrap before adding the cheese sauce and microwave on full power for about 10 minutes (be careful, it will be hot when removing the plastic wrap). Add the cheese sauce and bake as directed for about 45-55 minutes.
- Additional cheese (cheddar or parmesan) can be sprinkled on top once the foil is removed if desired.
- Store leftovers in an airtight container for up to 4 days. Reheat in the oven or the microwave.
Nutrition Information
Nutrition information provided is an estimate and will vary based on cooking methods and brands of ingredients used.
Course Side Dish
Cuisine American, French© SpendWithPennies.com. Content and photographs are copyright protected. Sharing of this recipe is both encouraged and appreciated. Copying and/or pasting full recipes to any social media is strictly prohibited. Please view my photo use policy here.
Can I use cornstarch instead of flour to make it gluten free?
Hi Bev, that should work well in this recipe. To prevent clumping you may want to mix the cornstarch with a small amount of cool liquid before adding it to the butter.
Could you use heavy cream or 1/2 + 1/2 in place of milk to make it creamier? Or is it not necessary….
I find it creamy enough as is, so I haven’t tried this recipe with either, but other readers have with great results with both! We would love to hear how it turns out for you!
Can I sub out oat milk for the milk?
Hi Marci, we have never tried this recipe with oat milk but would love to hear how it turns out for you! We use dairy milk as it adds a creaminess to the cheese sauce.
I used extra sharp white cheddar and Gruyère, which was a good mix. Also used a vidalia onion, the whole dish seemed overpowered by it unfortunately and that’s why I gave the dish only three stars. Potatoes Au gratin should not be dominated by onion in my opinion.
Sorry to hear that, Kris. We used a white onion and enjoyed the flavor but you can definitely reduce the onion in this recipe to balance the flavors better for you.
Trying this out today! I’ve never made potatoes au gratin (I’ve eaten plenty of ’em), so I’m excited. So far, smells GOOD!
luv the potatoes with cheese
Love this! The proportion are spot on. Book marked this one!
Creamy and delicious. We loved this dish. We’ll definitely be making this again and for all of our special occassion dinners. I used russet potaoes, a good quality locally made medium cheddar and parmigiano reggiano. As well, I used Earth’s Own unsweetend almond milk. Potato Pefection.
I used a larger baking dish and laid the potatoes flat. Also sauteed the onion (I used a red one) a bit first. Potatoes were tender and done in 45 minutes. I went back for 2nds and my dd’s boyfriend went back for thirds. Good stuff!
That is so great, Sue! So happy to hear this recipe was such a hit :)
Made this for dinner tonight. I didn’t change anything, I happen to have a white sharp cheddar waiting for this dish! I also used gold Yukon potatoes. My husband and I both had seconds. It was delicious!!
I have made these three times. I use russet potatoes. They turn out perfectly every time. Everyone loves them! Just remember they take a while.
I have made these three times. I use russet potatoes. They turn out perfectly every time. Everyone loves them!
These were superb! I did microwave the potatoes/ onions for 5 minutes, since my work had been interrupted. I really liked the result of standing the slices, rather than layering flat as usual
I made this last night for Christmas Eve dinner today when I took it out the liquid came out of the potatoes. Is this okay? I’m nervous because this is a staple in our dinner tonight I won’t be baking it for a few hours so I want to make sure I don’t need to remake the whole thing while I have time!
Also I did not bake it yesterday just pre made it exactly as the recipe said too!
I have made this ahead before and haven’t had it be runny so I can’t say for sure why it’s watery. If there is a little bit of liquid, it should be fine as some will evaporate in the oven. If there is a lot of liquid separated on top you might like to drain a little bit of it. Hopefully, it turns out perfectly for you. Merry Christmas.
How long should I bake it if I make it the day before ???
Still 90 min ?
It was unclear , sorry
Hi Miranda, I would let the casserole sit to warm up while the oven preheats and then bake it according to the recipe instructions.
Can these be made with other potatoes such as yellow or russet?
Yes it can. You can find this information in the post as well:
Just like when making scalloped potatoes, the best potatoes for gratin are red-skinned or Yukon gold potatoes. These two waxy potatoes can hold their shape well and because they’re thin-skinned, they do not require peeling (extra bonus!).
While russet potatoes or baking potatoes taste good, they’re more starchy. They do not hold their shape as well and the dish can become mushy, they’re more suited to mashed potatoes.
Are you supposed to stack the potatoes on their sides in the dish or flat, stacked on top of each other?
We stack them on their sides for this recipe
I’ve tried several of your recipes on my family and we have loved everyone of them our favorites are anything with cheese.
Thank you so much for all the great food recipes.
Can this be prepared day before then baked next day
Yes, it can be baked the next day.
I think one tip would be that you should add a layer of sauce between the layers like you do when baking a lasagna.
That is a great tip, Amy! Thanks for sharing.
I rarely write reviews but I have to give this one five stars, I’ve made it several times over the last six months or so, and it comes out amazing each time. I’m making this again to bring to my family’s Thanksgiving dinner! Thanks for a great recipe!
That will be a delicious addition to Thanksgiving Dinner, Hattie! So happy to hear you are enjoying this recipe!