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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Excited to make this. Should I use salted or unsalted butter?
I use you can use either. I most often use salted butter in cooking and salt to taste while I use unsalted butter in baking.
I love your recipes, I’ve made several. Would you please include your recommended pan size for the original recipe? It would help to have a starting place on what size pan is needed for both the original and if we double/triple the recipe etc. Thanks!
Hi Kerry, for this recipe we use a round 10″ casserole dish (intended for quiche). If doubling this recipe, I would use a 9×13.
Love these Au Gratin potatoes!!! Thanks, can’t wait to try some of your other recipes!
Didn’t notice the salt and pepper to taste step and the dish came out flavorless. Family is seasoning it as they go. I wanted this to be awesome.
Oh no, I am sorry to hear that AnneMarie! For more flavor, you can try using an aged cheddar as well.
This looks wonderful! Any suggestions if I could prep the day before and bake the next day?
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.
Phenomenal dish! The texture with the crispy edges and soft potatoes was perfect. I added about a 1/4 cup of jalapeno jack cheese for some heat but otherwise followed the recipe exactly. Used a mandoline on the smallest setting for the potatoes and onions. Everyone at the dinner table raved about it.
DELICIOUS DISH!
Hello! I am planning on making this to take camping next week. Do you think I could freeze it after putting the cheese sauce on before baking? Or should partially bake it then freeze it? Thanks!
That sounds like a delicious camping meal, Becky! I have never tried freezing this recipe, so if you do please let us know how it turns out. It would probably be best to prebake this recipe or at least partially bake before freezing but let us know how it turns out for you!
The microwave tip was brilliant!
Great recipe and I’ve added it to my collection of staples. Thanks!
The the flavor and presentation were terrific. Unfortunately my potatoes never completely softened. I put them back in the oven for a total cook time of 2 hours and 30 minutes. I used my food processor to slice the potatoes so I’m not sure what happened. I will try it again and hope for better results next time.
OMG this recipe is superb! Highly recommend and wouldn’t change a thing!
Delicious, easy and a very pretty dish.
I usually try to do my recipes by weight to be more precise. Might not matter too much in this recipe, I do a lot more baking than cooking… Is 1 cup of shredded cheese the same by weight (i.e. 8 oz)? Or would it be less?
1 cup of shredded cheese would weigh approximately 4 oz.
I would like to make these potatoes for Easter. However my ham needs to bake at 250 degrees and the potatoes at 400 degrees. Can I bake these at a lower temperature for a longer time and finish under the broiler to get the crunchy bits? How long would the take?
I can’t say for sure because I haven’t baked them at 250F, but I would think they’d take about 2-2 ½ hours, plus the time at the end uncovered at the higher temperature (while the ham rests). You’ll have to check them for doneness. Let us know how it works for you if you try it Angela.
I have made this recipe the last few Easters. I actually par bake or fully bake the day before and then just re heat (or finish baking) them with the ham. Just be sure to add a bit of extra milk prior to reheating and cover tightly with foil
Thank-you both!
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Do you use whole milk or evaporated milk?? I plan to make for Easter dinner 2021. They look so delicious!!
We use regular milk, but both will work. Enjoy!
Will half and half work in place of the milk?
Hi Mary, I have not tried this recipe with half and half but other readers have with success.
The regular directions say to cook covered for 60 then remove the tin foil and cook longer. When you are cooking in the microwave to cut down on time, do you ever take the foils off in the oven or leave it on for the 45-55 minutes?
Yes Meaghan, as mentioned in step 5, bake the last 20-30 minutes uncovered.
These are still baking, I can’t wait! Please add “sharp cheddar” to your ingredient list. It’s only mentioned further down the recipe so I bought mild cheddar. :-/ I was grocery shopping off the list of ingredients… thank you!!!
Made them for a party – were a HUGE hit. Great tasting!