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.
I don’t get the red potato part. Can someone please help me out. The only red potatoes I’ve ever seen are tiny. How am I supposed to make decent-sized slices?
If you can’t find medium-sized red potatoes, you can also use Yukon gold potatoes.
I’m cooking a picnic ham at 350…is it possible to cook this at 350 but maybe longer?
I haven’t tried it so I can’t say for sure Kim, but that should work just fine it will just take a little longer. If you try it I would love to hear how it turns out!
1st time making au gratin potatoes.
They turned out amazing with this recipe.
*I did sub provolone for guyere because that’s what I had
The cheese sauce can be made in the microwave. Microwave butter in a glass measuring cup on med high until melted – about 1 minute Blend in flour salt seasonings and milk. MW again until sauce boils and thickens, stirring once. For 2 cups probably takes about 3 minutes. Stir in cheese until melted.
Super yummy A little time consuming to prepare but well worth it
I forgot to rate the recipe I give it five stars
I used 3:1 gruyere to cheddar & the flavor of the gruyere is so rich and delicious!! I’ve made this several times and never had leftovers! Thank you for your insight and tips!
I used a combination of cheddar, gruyere, swiss and fiesta blend shredded totaling 2 cups. Absolutely delicious. My family was loved it. Pared it with a pork loin in air fryer and fresh green beans.
I don’t write reviews…
And I’ve never had luck with making potatoes like this (scalloped, au gratin, etc.). I don’t know if my expectations were out of whack or my timing off or things were cut too thick. Anyways…
This recipe was awesome! I had a bag of Cabot preshredded extra sharp white cheddar cheese and I used half & half for the milk. I used two onions too. Potatoes and onions were sliced via my mandolin. I took the microwave shortcut and made the cheese sauce while that was happening.
The whole dish was amazing! So good I want to make it again ASAP. We had 4 adults total for dinner and it was wiped out. Green vegetables were cast aside completely and I was ok with that. Thanks for this recipe. Mmm.
I am so happy to hear this recipe was a hit Lizzie!
I had a bag of red Yukon potatoes and a bunch of leftover Christmas ham to use up, and this was a perfect recipe for that. I did that sort of potato spiral around the rim of the dish and had most of the ham and onions in the middle, topped with a few more thin slices of potatoes. Having the edges of the potatoes poking out of the sauce gave them a great caramelization and texture. The 2:1 ratio of cheddar to gruyere, plus the honey-baked ham, gave a great flavor to the dish. This one is definitely staying in the repertoire. I had to get a little pokey with a knife after taking the foil off to make sure the sauce got between all the slices and to lift them out a bit. No notes. Great recipe! Thank you, Holly!
I am so glad you loved this recipe Jeremy!
I made this one day in advance (Christmas Eve), baked it for one hour and then I let it come to room temperature on a rack. I covered it in foil and threw it in the fridge. The next day I pulled it out of the fridge about 45 minutes before I was going to finish it off, then tossed it in the oven for about half an hour, removing the foil about halfway through that time. It came out perfect and everyone loved it. I almost doubled the recipe.
For the prep, I did it exactly how you described. I broke out the mandolin (scariest kitchen tool ever) and sliced up the potatoes and onion and made little stacks. I used gruyere and extra sharp cheddar for the sauce. I totally agree that this is creamy enough made with the milk and roux. Thank you for sharing this outstanding recipe. It’s a keeper for sure.
This dish, while very time consuming, was delicious. I do not know if I will make this “labor of love” except for a special occasion again. ( I made it for Christmas dinner with my husband’s help).
Very complete directions rarely done as well. Very good recipe. Thank you had to go over many times and site did not block you!
It’s not out of the oven yet, but pre-cooking this morning to go with our Prime Rib for dinner and OH THIS CHEESE SAUCE. Dishwasher will have an easy job since I locked the pan and whisk clean. I added some herbs, garlic, and a good bit of chunky fresh ground pepper. Can’t wait until dinner!
Mine was soo liquidy I made it the day before to save time for Christmas Eve day, ideas? Flavor is great!! Just lots of fluid when I pulled it out of the fridge that didn’t absorb during cooking
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 turned out perfectly for you.
This cheese sauce is to die for! My husband and I pre-made it together for Christmas dinner tomorrow. We used heavy cream instead of milk, Tillamook Cheddar for the base cheese, and tweaked that up by substituting Yancey’s Fancy Smoked Gouda with Bacon, for the Gruyere cheese in the recipe, and no other subs or additions. If I’d used Gruyere, I would’ve added crumbled bacon anyway for a little smokiness (because that’s how we do down here in Georgia), but with the Smoked Gouda with Bacon I didn’t need a single other seasoning besides what the recipe calls for to get a powerful punch of flavor, a savory and creamy cheese sauce. I will definitely use this cheese sauce again for Mac & Cheese and I’ll try Yancey’s Fancy Champagne Cheddar to get a mellower, more sublime cheese sauce. Yum!!!
Why use milk instead of heavy cream?
This recipe starts with a basic white sauce which uses milk, the cheese adds additional richness so I find the milk to be creamy enough.
Would russet potatoes work with this recipe?
Russet potatoes will work but they don’t hold their shape and tend to fall apart.
Wow, I’ve been using this recipe for at least 15 years, back when we printed everything and put it in a book! My cookbook is packed so thought I’d try to find the recipe. Much to my surprise and delight, it’s still here!! First rate!!!
If I want to add fresh thyme and Rosemary, how much should I use. I want the flavor to be subtle.
For a subtle flavor I would suggest about 1 teaspoon of each.
Can I make this a day ahead
I haven’t tried this exact recipe ahead of time but I have made scalloped potatoes ahead successfully so I do think it should work. Prepare as directed and cool. Once cool, cover with plastic wrap and refrigerate. I would suggest removing from the fridge at least 30 minutes before baking. It may need a little bit extra cooktime.
I’m wondering if I can cook it ahead of time and reheat. Or perhaps partially cook it (say an hour) and finish it off the next day
I haven’t tried cooking this recipe part way but I think that would work.