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.
This post may contain affiliate links. Please read our disclosure policy.
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 love your recipes and have made many of them! I have a question about baking dish size please. I have a ceramic 13x9x4 baking dish (I believe that is 3-3.5 qt?) is this too large for the 8 servings? I dont have a 2.5qt. as is called for.
Thank you!
That would be a little too big as it would make the layer thinner. You could also line a partition in the pan with heavy duty foil. I hope that helps!
I have made this recipe a few times, and it is always tasty, but it’s also somewhat inconsistent. The main reason why, I think, is because of the way the cheese is measured. It would help if the quantities were given in ounces rather than grated cups, which is not a consistent measurement from cheese to cheese (they all grate differently and fill differing proportions of space within a measuring cup).
Thank you for the suggestion, Bettina! I can definitely see how that would help. :)
We have been making your recipe for a couple years now.
Followed instructions and it is fabulous.
I can’t even begin to tell you how impressive of this dish is to serve and how our guests have always been extremely impressed by it.
This year took the liberty to add a little bit of time to the cheese sauce and again beyond fabulous.
I cannot thank you enough!
So happy to hear how much you love this potatoes au gratin dish Lisa!
A must make ♡
For the make ahead instructions, when it says it can be made 24 hours ahead of time and then cooked for longer, does it mean to make the entire recipe and then reheat it? Or to make the recipe up until the point of baking, refrigerate it and then do the baking just the once?
Made this recipe MANY times and always happy!
Hi Damien, we prepare this with sauce right up until just before the point of baking, then cover and put in the fridge.
This is the only scalloped potatoes recipe I use, and we love it! My question is, has anyone done it in the slow cooker? I’d like to try that next time, but don’t want to wreck a great thing….
I haven’t tried this recipe in a slow cooker so I can’t say for sure – dairy doesn’t always hold up in the slow cooker. I use this recipe for making slow cooker potatoes though.
Absolutely fabulous recipe. I followed pretty close. I did not have milk, so I used some watered down, cream, half and half and a bit of sour cream. It still was delicious. I did not have gruyere, but used baby swiss and sharp cheddar. It looks just like the picture and taste absolutely amazing. oppps….no dry mustard, subed dijon. Hands down one the the best recipes!!! Thank you.
I’ve made this several times now and my husband keeps asking for it!
I have a couple people in my family who hate onions. Can I substitute onion powder?
You sure can! I would recommend about 1 teaspoon added to the sauce.
this recipe has been a hit every time I’ve made this friends and family always ask me to make it again .
Delicious recipe! Made for the first time and turned out great.
I’m trying this recipe today for Easter Dinner. You mentioned you use Parmesan cheese, how much do you use? And do you add it in when melting the other cheese? Thanks!
I sprinkle it on top, about 3 tablespoons.
Can I make this recipe the day before baking it?
It looks delicious!!!!
Yes, the prep ahead directions are listed in the post. Enjoy and let us know how it goes!
This dish can be made 24 hours in advance. Ensure the potatoes are completely covered in the sauce—any exposed bits of potatoes will discolor slightly. Cover tightly with plastic wrap and refrigerate.
Remove from the fridge at least 30 minutes before baking. You may need to add 10 to 20 minutes to the baking time.
Has anyone tried to bake ahead for the 60 minutes, refrigerate, and then bake the last 20 uncovered at a later time? I want to make ahead to bring for Easter, and think I would have to bake uncovered longer if it starts cold.
Potatoes hold their heat for quite a while so if you’d like you can allow for extra time. If they’re ready early, they should keep warm for a while.
easy, delicious, quick enough for busy days
I live with and help take care of my grandparents. Very thankful for Holly and her recipes, as she helps me with many meals!
These potatoes were the best my grandparents and I have ever had! They wanted to make sure I told Holly thank you!
Beautiful but not much flavor as written. I will either throw out the rest or melt cheese on top of each serving to save it. Very disappointing.
Hi Patti, sorry to hear that you didn’t enjoy this as much as we do. Did you use both cheddar and gruyere?
I want to try this recipe, it looks delicious! The only Gruyere I was able to find was very expensive. Do you think Cheddar and Gouda would work instead of Cheddar and Gruyere?
Hi Vivian, swiss cheese is a good replacement for gruyere. You can try gouda or a white sharp cheddar. It will change the flavor but it will still be delicious.
Outstanding receipe. Always receiving compliments when I make this! One question – What is considered a serving? Is it a cup, 1/2 cup? thank you
The nutritional information is for ⅛th of the recipe.
This was really good.A little time consuming, even with using a mandolin, but it was fun, making the stocks with the hubby. However, I did not care for my choice of cheeses. I used Gruyere and Swiss. The Gruyere was good, the Swiss not so much (super stringy) And I also used pre-shredded cheese, won’t be doing that again! My only problem was that the cheese sauce burned on the bottom. I didn’t think that would have happened since it was covered in foil for the first hour of cooking. I used a glass baking dish. Any thoughts on what might have happened?
The potatoes au gratin recipe is versatile so feel free to change up the cheeses to your liking (cheddar and gruyere is a great combo). I haven’t had the cheese burn in the bottom but generally bake on the middle rack in a ceramic dish similar to this one. I hope that helps!
Pre shredded cheese has a coating on it (maybe flour or cornstarch) so that it stays separated which changes the consistency when melted. We make fondue regularly and the recipe warns of using the pre shredded kind.
This recipe is absolute fire! It was such a hit with my family and probably the best potatoes I have ever had. 5 stars +++++