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.
Wonderful, so good had it lunch time and with my evening meal. The smell when cooking is to die for. 10/10
I’m so glad you loved it Linda!!
I love au gratin potatoes, but I’ve never been able to find a recipe online that sounded as good as my mom’s (too many have nutmeg or other strange things in them — she just used red bell peppers). This one isn’t the same, but it looks incredible. I’m going to make it later this week, and I’m definitely including a link to it in my Thanksgiving recipe roundup. Thanks in advance!!!!!
Enjoy Carolyn!
When you say slice the onions as thin as possible . Do you mean in the baking pan rotate onion slices and potato slices? I want to make your re ipie, but I am unclear of the placement of the onions.
Thanks
Yes, the onions are in between the potato slices. You can see them in the photo just above the recipe.
I made it. Didnt have Cheese you suggested so i used some velvetta, sharp and mac & cheese mix. They were delicious.
What size pan 9×13?
My dish was a round 10″ casserole dish (intended for quiche).
Very good.
So glad you enjoyed it!
Can I use white cheddar in place Of the gruyere cheese?
We love to sub the gruyere for a swiss or provolone but a white cheddar sounds delicious too Reylene!
Hi Holly,
I do not know how to pin things from your website.
I have my pinterst all set up with boards organized but don’t seem to know how from your site.
Can you help me with this?
Thank You!
Trina
If you are on a desktop computer, you can click on any photo to pin. If you are on a mobile device such as a phone, you’ll need to gently double click an image to pin it. You can also find all of my recipes here to repin. I hope that helps!
This was a great side dish. Love the cheese sauce. I will make it again when my children visits.
a clove of garlic minced and 1/2 tsp nutmeg make these au gratin the best fall and holiday potatoes for the season. perfect with ham…
Potatoes washed and sliced…. ready to bake this beautiful dish for tomorrow’s Christmas dinner.
This looks amazing! And I just happen to have a block of gruyere that needs used up. Would this dish work with Russet potatoes, since that’s what I have on hand? Or do I need to buy red potatoes?
Russet should work just fine in this recipe.
This looks delicious! I have a big catering event next month and was going to make this for the side. It is a luncheon so everything needs to be done early. Do you think this could be prepped ahead of time and baked the next day? Or should I bake the first section of it the day before and then refrigerate it and cheese/bake it the last 20 to 30 minutes the day of?
I have only made this recipe as written so I can’t say for sure.
At what temperature are you baking these incredibly luscious looking au gratin potatoes?
Oh thank you so much Deb, sorry I missed that! Bake at 400 degrees.
This is so yummy looking. Just a little tip, a lot of plastic wraps are not MW safe, better to use a glass lid, or improvise a cover that would be MW safe.
Thanks Barbara! Great tip, I’ll have to double check mine!
I do not have dry mustard can I use just plain mustard
It will change the taste a little, but you can substitute it. Enjoy Joanne!
gruyere cheese!! Delicious. This would turn any potato dish into the BEST. No one could hate gratin potatoes they are like a gift from the god. This definitely looks next level.
Ummm, this gratin potato dish is making me hungry even though I just ate dinner!!!
This looks amazing!! One of my favorite dishes and surprisingly one that is so easy to mess up. Yours is perfect!!
Oh I am drooling over here!! This looks DIVINE!
Music to my ears! Cheese is my livelihood! :) This looks and sounds amazing! Can’t wait to try it!
These look absolutely amazing. A keeper recipe for sure!