Cheesy, rich and totally decadent, au gratin potatoes are always welcome on my table. While they are most revered as a side dish, I could eat them as my entrée and be perfectly content. This easy potatoes au gratin recipe has so many variations that you will literally never make the same batch twice.
Sometimes referred to as Dauphinoise, these are the ultimate of potato sides.
Au Gratin vs Scalloped
First, let’s discuss one of the most common mistakes made in cooking next to aioli: what is the difference between au gratin potatoes and scalloped potatoes? It is really easy: CHEESE.
Scalloped potatoes are baked in a cream sauce, basically a seasoned roux, while au gratin potatoes are made with a cheese sauce- the roux with cheese.
I love both, but if I have the choice to add cheese, why in the world wouldn’t I?
I am going out on a limb here and saying that nearly all cheese sauces start with a roux, which is combination of fat and thickener, in most cases butter and flour, then thinned with milk.
This mother sauce is the base for everything from jambalaya to cheese sauce that will grace broccoli, mac and cheese, dipping sauces and of course, au gratin potatoes.
The beauty of a nice roux is that it is a blank slate waiting for the cheese to give it personality and flavor. While for this recipe we choose a classic cheddar cheese, this is one of the many ways you can customize, by swapping a different cheese. Even use a blend, cleaning out the cheese drawer.
What potatoes are best for potatoes au gratin? Another simple easy- statchy ones. They have a low moisture content so excess liquid won’t thin out the cheese sauce, and a raw gritty flesh that gets creamy when cooked.
The starch not only helps to thicken the cheese sauce and bind it all together, they can withstand long cooking times. Since this potato casserole is essentially a brick of potato, it needs 1 hour or more to be fork tender.
The most common starchy potatoes are Yukon Gold, Russets or Idaho potatoes. The downside is that these varieties also have thick and hard to chew skins, so you will have to peel them before using.
Cutting the Potatoes
While you can go the good, old fashioned route and try your hand at uniform slices with a handheld knife, you can can also use a food processor or mandoline slicer.
Having your potatoes slices be as close to the same thickness as possible will help them cook evenly. These tools also just make the process fast.
Au Gratin Potatoes Ingredients
- Potatoes– Read above, starchy potatoes, about 4-5.
- Unsalted butter- if using salted, omit salt below.
- Flour– all-purpose flour works best, but flour alternatives can be used as long as they have thickening properties. ‘
- Milk- dishes like this aren’t really supposed to be “skinny” and therefore I don’t skimp on the milk. Full fat for me! It will work with a lower fat content, but it may not be as thick with less fat.
- Seasonings– coarse Kosher salt, bay leaf, garlic powder, onion powder and white pepper. Any of these are optional and can be increased depending on your taste.
- Cheese- See above under the section on roux, we used sharp cheddar cheese for these au gratin potatoes, but nearly any harder cheese that melts well can be substituted. Swiss, white cheddar, pepper jack, Monterey jack, gouda are my others favorites.
This dish is a little more time consuming than most of our recipes, but it is totally worth it.
- In a small saucepan, melt the butter and whisk with flour until a paste forms. This is the base of the roux. While whisking, add the milk. Add the seasonings and bring to a low simmer. This achieves several goals: scalds the milk so the sauce is thicker, heats so that the cheese can melt in smoothly, infuses the sauces with flavor from the bay leaf and other seasonings and thickens.
- After the milk mixture comes to a low simmer, whisk in the shredded cheese until smooth. Turn off the heat and allow to cool slightly before using.
- Meanwhile, start to prep the potatoes. Fill a large mixing bowl with cold water and a little bit of salt. Placing the potatoes in this mixture will prevent them from browning. Browning doesn’t impact the flavor, but is unsightly.
- Peel the potatoes using a Y peeler, then cut to 1/4 or less thickness using your desired cutting method as described above.
- Grease a baking dish and then place half of the sliced potatoes in the bottom, topping half of the cheese sauce. Top with the remainder of the potatoes and then cheese sauce. Cover with aluminum foil and bake.
- Remove from the oven and take the cover off, sprinkle with the remaining cheese. Return to the oven for cheese to melt.
- Now is the hardest part… allow the au gratin potatoes to sit. Much like meat, they need to rest in order for the sauce and liquids to reabsorb into the dish. Slicing immediately will most certainly result in them being delicious, but not suitable for a plate, more like a bowl situation.
Au Gratin Potatoes Variations
You’ll never make the same batch twice!
- Add bacon- because bacon makes everything better. Mix about 1/2 cup of crumbled bacon into the cheese sauce when it is complete.
- Real onion– Saute some leeks or white onion and fold it into the cheese sauce. Also top with scallions or chives.
- Roasted garlic– the smoky flavors from roasted garlic can’t be beat. Roast and smash a whole head and add it to the cheese sauce.
- Heat- add a little spice by adding chopped jalapenos to the cheese sauce and swapping the cheese for pepper jack.
- Smoky– Smoked paprika and smoked cheeses will give this recipe a hint of flavor unusual for potatoes.
Make Ahead, Storage & Freezing
The good news is that even though these au gratin potatoes take a little time and elbow grease to make, they are also make ahead friendly. My husband might even tell you that leftovers the next day are even more delicious than the fresh potato casserole.
Make up to one day ahead of time. Store covered and in the refrigerator for up to 5 days. Leftovers can be reheated in the oven or the microwave, but be mindful that high temps in the microwave can make the cheese sauce separate and look oily.
To freeze, follow our instructions for how to freeze a casserole. To cook, cook from frozen at 350°F, covered for up to one hour or until the center is hot. It might require a fresh topping of shredded cheese to freshen it up.
More Potato Dishes:
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Au Gratin Potatoes
- Preheat oven to 350°F. Coat a 3 quart casserole dish with cooking spray. Set aside.
- In a small saucepan, melt the butter and then whisk with flour until it forms a paste. While whisking, pour in milk until smooth. Add the bay leaf, salt, pepper, onion and garlic powder. Bring to a low simmer.
- Remove the saucepan from heat and whisk in 2 cups of the cheese. Whisk until cheese has melted and sauce thickens. Set aside.
- Peel potatoes and evenly slice to 1/4 inch or less thick. Place in cold ice water to prevent browning (optional).
- Remove the bay leaf from cheese sauce.
- Place half of the sliced potatoes in the prepared baking dish. Pour half of the cheese sauce over the top. Add remaining potatoes and top with the remaining cheese sauce. Cover tightly with aluminum foil.
- Bake covered for 60 minutes.
- Take the baking dish out of the oven and remove the aluminum foil. Top with the remaining 1/2 cup of shredded cheddar cheese and return to the oven uncovered. Bake for an additional 20 minutes or until potatoes are soft the whole way through.
- Remove and allow to sit for 15 minutes before slicing and serving.
- Optionally, top with additional salt and pepper, bacon, scallions or chives.
- If you've tried this recipe, come back and let us know how it was in the comments or ratings.