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.
In the oven as we speak, doubled the recipe ♀️
Such a delightful and detailed recipe! I love the helpful tips like using a mandoline for even slices and the make-ahead instructions. Can’t wait to try this creamy, cheesy goodness for a cozy family dinner
So this is the fourth or fifth time I’ve made this recipe. Each time I’ve changed it slightly. Easter, I think I had it perfect. I substituted Scallions for onions (sweeter) and used 1 1/2 cups Gruyere and 1/2 cup finely grated Parmesan; finally, I substituted one of the cups of milk with buttermilk and added a tablespoon of Garlic and a teaspoon of Italian herbs. It’s absolutely amazing. It has a bit more flavor than the basic recipe, but is not overpowering at all.
this recipe is amazing! Thank you for sharing!
When preparing these a day in advance advance, do you bake the dish after you pour the cheese sauce on since the potatoes are now warmed from the cheese sauce and simply reheat the next day, or cover the raw potatoes with the hot cheese sauce, immediately refrigerate and then bake the next day? Thank you!
When making in advance, as long as the potatoes are completely covered in the sauce you do not need to bake it first. I generally pour the sauce overtop and cool slightly (while I clean up) before refrigerating. Remove from the fridge at least 30 minutes before baking adding 10 to 20 minutes to the baking time in the recipe.
Made this once and making again tonight my boyfriend requested is as I’ll be out of town and he wanted this dish to snack on. First time around was a success so will this! Thank you!
Thanks for this recipe. I cooked baked potatoes using your recipe for the oven. I then used this recipe and added a can of cream of mushroom soup for the sauce and threw in some crawfish. We served it on top of the baked potatoes. It was absolutely delicious. It was served on the side of your braised thighs with mushrooms.
I 4x the recipe for a 10lb bag of potatoes and it turned out perfect.
brilliant
Thank you, Kevin. I am glad you enjoyed it.
I thought at first it was a little time consuming but now I don’t mind it at all, worth the time!! It’s so delicious. I’ll be making it many more times I’m sure ❤️❤️❤️
this is wonderful, I added some carrots, cauliflower and broccoli.. great dinner!!
I made these exactly as written, and they were amazing! Everyone commented on how good they were, and there was none left.
I made this for a 50s dinner party. I had never made this dish before. I was a big success. I forgot the mustard. And next time I will make more cheese sauce.
excellent
very nice l add a little cheese
Amazing recipe!!!
These tasted bland. I used Yukon gold potatoes and omitted the onions. I added rosemary to the cheese sauce for some extra flavor. I did shred my own cheeses as well. Not sure what happened.
omitting the onions is the mistake. onions give the best flavor to most dishes. If your not an onion fan just chop them up in a electric chopper until basically mush almost liquefied then add it. you won’t notice the onion but the flavor will be there.
These potatoes are fantastic. My family wanted a potato dish for Easter and I chose this one after searching online. I am not crazy about potatoes but I had two helpings.
I used a combination of Cheddar , Swiss and Parmesan . I used pre shredded- my brand doesn’t have any additives so no problems with melting .
Can I use heavy cream instead of milk?
I haven’t tried it so can’t say for certain but it will likely be a bit thicker with heavy cream. You could substitute half with low sodium broth as well. If you do use heavy cream and it’s too thick, you can thin it out with a bit of water or broth. Let us know how it goes!
Made this today. It was great.i included some chopped bell pepper.