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.
followed recipe to the letter- potatoes were severely under-done (and I know my oven temp is accurate). I sliced yukon golds to 3mm thickness (you can see light through them) with the mandoline. They needed an additional 30 minutes beyond the additional 20 minutes the recipe indicated to brown them. Check your potatoes – pull one from the middle before you serve them to make sure they’re cooked.
Sorry this recipe took longer for you, Matt. I hope you still enjoyed the taste!
Great!
delicious! I added fresh thyme and some garlic for extra flavor. I will be making these again!
Simple recipe to follow and was so delicious! I added fresh thyme and some garlic for extra flavor. I will be making these again!
This tasted very bland. It needed a lot more seasoning. Next time I will season the potatoes, and just add more seasoning overall
Thanks for trying this recipe, Ryan.
Made it and thought there would be leftovers . Nope !! Will definitely be my go to for pot luck dinner next week .
I made this today. I love onions but not in this dish. the dish is very good but I felt like it was missing something. maybe garlic or some bacon.
We recently moved back to my hometown to be near family, and my husband loves this style of potato, so I ran with a new recipe for our inaugural debut spread. I got all excellent reviews from my 79-year young father all the way down to my 5-year old niece. I did a double batch and was a little worried, but baked it in a lasagna pan and baked an extra 10 minutes on the front side, and it turned out great! My husband wants more sauce next time, and that’s an easy fix. It makes a large dish, so I will just shorten the potatoes by a few ounces.
Delicious!
So happy to hear that, KJ! That’s the perfect debut ❤️
I prepared this dish as suggested. We broke the madelin, but luckily I had newly sharpened knives and was able to complete the recipe easily. The red potatoes were really easy to slice. I couldn’t find my round dish, but my rectangular dish worked perfectly. I added about a fourth of a cup of melted butter to the dish just before serving (it didn’t need it!} but my husband loves butter! The dish was beautiful and equally delicious! I promised my son I will make it again!
Thank you Holly!
This recipe, although a little labor intensive, is delicious. My husband really enjoyed them… one of his favorites. I do t typically like potatoes prepared this way, but did really like this recipe. Thank you.
Wow, amazing. The first time I’ve made these and the potatoes are cooked! I used a mandolin, that is the trick. I added 3/4 tsp garlic powder. No salt was added. This is definitely being saved. Next time I will add chopped bacon and jalapenos! Thank you thank you thank you.
These au gratin red potatoes “rocked our world”! I had some medium red potatoes for smashed potatoes, which we always love, but I wanted to try something different. They’re a little extra work, but worth the effort, for sure! Delish! Used my mandolin to slice – a must for easier prep. Thank you for this recipe! I will be using it for Holiday dinners too!
I used pepper cheese & instant potatoes to thicken my cheese sauce. I poured said cheese sauce over pre-cooked (red potatoes) I had leftover in the fridge. Added 1/2 Vadalia onion and 1/2 cup chopped green onions & covered everything in nearly expired sliced American cheese (12 slices). The coup de gras was chopped up deli ham meat over the cheese. 400° for 40 minutes was perfect. Delicious meal !!!
Sounds wonderful Joseph!
the absolute BEST gratin i’ve ever made! we subbed out the gruyère for swiss and it tasted stellar! never had this dish with onions but i will only be making it this way from now on.
Had a dinner party of 10 people and 10 out of 10 loved these potatoes. Need I say more???
This is fabulous!
Easy and I love the fact that it can be made a day ahead.
Varied the cheese to 1 C white sharp cheddar, 1/2 C Gruyere and 1/2 C Colby Jack and added minced garlic to the rue. I will definitely be making this again!
If I wanted to make a truffled version of this could I put a tablespoon or so in the cheese sauce? Wondering if others thought this would go well with the recipe
I haven’t tried it so I can’t say for sure Cheesy, but I think that sounds wonderful! If you try it I would love to hear how it turns out!
It’s spelled roux
This recipe was easy, tasty, and versatile! The cheese can be different, and it can be seasoned in a variety of ways. It is indeed easy and cheesy… :-)
I’m the cook that needs a recipe and hope it turns out, mostly does. I followed this as written and so impressed with this dish, yhe flavors were so good, my husband raved about it.