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.
Easy to make and delicious! No leftovers at our house.
These potatoes are the best I’ve had! Hands down! Made these just now for our Christmas Eve dinner and WOW!!! I seasoned the potatoes before hand and then added a little salt and pepper in the cheese sauce. Perfection!!! I wish I could post a picture because they look amazing!
So glad you loved them!! You can tag @spendpennies on Instagram, we’d love to see them!
Can one assemble this ahead of time, pop in the fridge and bake it later?
We would recommend baking it first and then cooling it completely. When you want to reheat it let it sit at room temperature for 30 minutes and bake uncovered for 35 or until heated throughout.
To reheat, bake for 35 minutes at what temp?
This, plus your ham recipe, will be center of our Christmas dinner!
I would reheat at 350°F. If you’re heating at a lower temperature (in the oven with ham) they’ll need a bit longer. You can also start the reheating in the microwave and then finish them off in the oven too.
What a beautiful dish! I loved the potatoes standing up. I used a large oval casserole dish (Le Cruset) and it made a beautiful presentation. Next time I will use 3 lbs of potatoes, two onions and double the sauce. I could have salted the more heavily. I used russet potatoes since I needed to use them up and they worked fine. Also, allow time; it took 30 minutes for assembly and then an hour and a half to cook. I did save some time but slicing the potatoes in my Cuisinart food processor.
I used peeled russet potatoes instead of red potatoes. Cooked them in a cast iron pan covered with foil for 60 minutes in the oven, then 30 minutes uncovered in the smoker. Amazing.
I love the idea of putting these in the smoker, thanks for sharing!
Scalloped refers to the thin slicing of the potatoes to make them resemble scales, as in scallop shells and scalloped borders, which in old English used to be “to collop“. Gratin is grated, as in grated cheese or grated bread, referring to the crust. I made this recipe with red potatoes and chopped ham. Delicious!
I just love your recipes.
Can’t wait to try these!
This is an excellent recipe. I’ve made it twice, using the quicker microwave method both times. It lends itself well to seasoning with additional flavors (garlic, rosemary, cracked red pepper, etc.). If you’re thinking of making it, I recommend a liberal amount of salt — potatoes need salt to taste right, and 2.5 lbs is a lot of mass to season. This dish also reheats really well in the microwave.
Great recipe. A few things- salt and pepper the potatoes before you stack them in the pan. Also sharp cheese will get you more flavor
OMG, these potatoes were amazing! Just made them tonight. Will definitely be added to the rotation! I used a mandolin to thinly slice the potatoes quickly, making this recipe super easy. Only had cheddar cheese so used 1.5 cups of cheddar, and it was delicious! Will continue to make this. Thnx!!
Followed the recipe as listed besides adding a couple dashes of roasted garlic to the mix. My husband said it reminded him of his moms said it was almost better! Thanks
This recipe is delicious! This recipe filled out my 8×8 Pyrex perfectly. Turning the potato slices on their sides is a great idea. We skipped the onion and added a fat tsp of Trader Joe’s onion salt here. Didn’t want slices of onion in the pan and the onion salt is actually not very salty at all and adds a bit of green from chives. I used nearly all sharp cheddar plus a couple heaping tbsp Parmesan. I sliced the potatoes to 1/8“ on my mandolin. I’m saving this one!
I have been craving potatoes au gratin for a couple of weeks now, and made this yesterday with a few substitutions: Gluten-free flour blend instead of AP flour, fresh snipped Rosemary rather than mustard, and I used whatever cheeses I had on hand (mostly Feta and some bits of leftover hard Italian chesses, sort of like Romano). I sprinkled my salt and fresh ground pepper onto the stacked potatoes rather than in the sauce (though I did add a little there, too), so I could better estimate how much I wanted; that’s just how my cooking brain works. ;)
I also added four sliced cloves of garlic, about half of the green tops of a leek for color and a little depth of flavour, and 1-2 tsp more butter. It was SO good! Honestly, it was even better the next day. I can’t stop eating it! :D
Thanks for the recipe! :)
Simply devine, I used very little onions for my taste.☺ I also used extra sharp cheddar and provolone cheese.
This dish can stand on its own with maybe a side salad. I served it with ribeyed steak and fresh steam stringbeans. Scrumptious!
Sounds like a delicious dinner Laura!
Fantastic. Had some red potatoes that needed to be used. Scrubbed them up and used the mandoline to slice. I made this decision late so I opted for the microwave short cut. It worked, but the sauce doesn’t ooze in between the potato slices as well (those starchy little bits try to rejoin). As it is quarantine time, I did not have lots of cheese options, I just used Colby Jack …. it was absolutely a hit, so pretty and delicious … next time I’ll do it with the proper cheeses, and bake for the full cooking time in the oven. Simple and amazing! Thanks.
This would be perfect except I have to guess at the size of the size of the casserole dish. An important detail given the upright orientation of the potatoes and onion slices.
We often use a dish between 1.5-2.5 QT’s but whatever size pan they fit in will work great Emery!
Excellent recipe! These were a big hit at the potluck. I used an apple-wood smoked gruyere and added some minced garlic into the cheese sauce. I did end up making a bit more sauce than what’s called for here. The stacking method makes for an attractive casserole especially with a sprinkle of paprika and fresh parsley on top! I was told I have to bring the ‘fancy potatoes’ to every gathering now lol.
P.S. I also used a mandolin to slice the potatoes and onion into thin medallions and it worked great!!
Made this for Valentine’s Day but altered recipe slightly: more butter, sub shallot, add flat leaf parsley, double gruyere. The hardest thing is estimating salt as the butter and cheese determine how much you need. Delightfully simple guised in sophistication. Def a winner. Minus 1 star: solid dish but didn’t have a WOW factor.
Im sorry but these were the worst cheesy potatoes I’ve ever made. No flavor at all.
Sorry to hear that Cathy! We love the flavor of this recipe, but you can definitely alter it to your preferences.