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
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I’m planning to make it for Easter. Should I use a 9×13 baking dish to double the recipe? Will it take longer to cook?
Hi Cathy, I would definitely use a 9×13 if doubling the recipe. I would adjust the cooking time slightly and cook for 75-90 minutes covered, then 25-30 minutes uncovered until lightly browned and the potatoes cooked through. I would love to hear how it turns out for you!
So good!! I would use the sharpest cheese you can for the most flavor!
I agree! I am so glad you enjoyed this recipe Delisa!
Delicious flavor as usual. My sauce was a touch thinner than I’d expected but tasty!
I used a mandoline as you suggest. The slicing went fast and potatoes were uniform.
I made this recipe the other day and wow! The funny thing is that I made it from someone else’s exact and I mean exact recipe under another name. I think someone may have copied Holly’s recipe and put it up as their own! Anyway, my husband and I enjoyed it beyond words! YUM! I make it just as written. The last time I made it I halved the recipe as there’s just the two of us. I regretted that as we ate it all up! Tonight when I searched it for the full recipe for 8 servings, I came across Holly’s and realized the recipe is definitely her recipe as I have used Holly’s recipes many times before. I do definitely recommend this recipe!
I’ve made it so many times and we love it ! Use a mandolin slicer , makes it easy.
I have made this many times…. Delicious!
Do you think this would work with dehydrated potatoes? I imagine you would need some extra liquid as it would need to be absorbed to rehydrate and cook the potatoes. Would you have any idea how much more liquid if this recipe were to be followed please? 💝
I do think it would work if they’re sliced. When we were young, my mom used to make dehydrated scalloped potatoes from a box all of the time. I agree that you would need liquid to rehydrate the potatoes but I don’t know how much. Is there any indication on your package of potatoes? You could also possibly look at the instructions on this box to get an idea of the ratio. Let us know how it goes!
No, I would use real potatoes!
I have made these every year for Christmas Day dinner and my family devours them! I follow the recipe as is, doubled, and they come out perfect every time! Thank you!
If I’m preparing this in advance, do I follow all the step and cook entirely or should I follow the steps up to adding cheese (before baking) then refrigerate overnight and add 10-15 minutes onto the cook time?
Hi Tiffany. I recommend to keep potatoes covered in sauce, cover tightly, and refrigerate before baking. Bring to room temperature before baking, and add 10–20 minutes to the bake time.
Can I make the cheese sauce ahead of time without adding it to the potatoes?
While I haven’t tried it that way, I think that should work. The cheese sauce will firm up in the fridge and should be gently heated before adding to the potatoes so it can be poured.
Are yellow Idaho potatoes suitable for this recipe?
Those will work just fine! Enjoy Marilynn.
Can this be made in the air fryer within a ceramic dish?
I haven’t tried it so I can’t say for sure Catherine. If you try it I would love to hear how it turns out!