The best Potatoes Au Gratin recipe combines thinly sliced potatoes and a creamy flavorful cheese sauce that gets baked to perfection with a crispy top.
There are a few things that set this recipe apart from the others. There's a trick to getting the most tender and best tasting potatoes that are loaded with flavor. You'll definitely want to make these next time you're craving cheesy potatoes!
Why this recipe works:
One of the most tasty side dish recipes you can make is Potatoes Au Gratin!
- With this recipe, the potatoes are sliced paper thin. That not only helps them cook to the point where they're perfectly tender, but each slice absorbs a bit of the flavorful cheese sauce.
- Sauteed onion and roasted garlic add a tremendous amount of flavor.
- The final dish looks amazing when you arrange the potato slices vertically. Scroll down and I'll show you how!
Ingredients needed to make Potatoes Au Gratin:
- Golden potatoes - I leave the skin on and slice them super thin
- Yellow onion - this will be sliced thin as well
- Butter, Flour, and Milk - this is the base for the cheese sauce
- Roasted garlic, dry mustard, freshly grated nutmeg - so much flavor!
- Cheddar cheese - freshly grated from a block works best
Here's how to make it:
I'll break the instructions up into two sections: the prep and how to bake.
How to prepare Potatoes Au Gratin:
- First step is to lightly scrub the potatoes and slice them super thin. I highly recommend using a mandolin for this step.
- You will soak the sliced potatoes in a large bowl of cold water for at least an hour. This is a cooking trick that isn't used as often as it should! Not only does a lot of the pasty starch get washed away, but the added water helps the potatoes steam while they cook which makes them super tender.
- Next you will melt the butter in a large pan and saute the onion until it is golden brown.
- Flour is sprinkled on top of the cooked mixture and allowed to cook. This will be the base of the roux.
- Add the milk and stir, over heat, until a gravy forms. Remove the hot mixture from the heat and stir in the mustard powder, roasted garlic, and shredded cheese.
- Stir the cheese sauce until all of the cheese has melted.
How to bake the potatoes:
This potatoes au gratin recipe is a combination of thinly sliced potatoes smothered in a cheese sauce and then baked. Here is the best way to do it.
- Drain the potato slices from the cold water and then arrange them upright in a greased baking dish.
- Cover with the cheese sauce.
- Use a spatula to spread the cheese sauce and ensure all of the potatoes are covered.
- Cover with a lid and bake for about 35 minutes. Remove the lid and continue baking for another 20-30 minutes until they get lightly browned.
Recommended cooking tips and substitutions:
- Potatoes - I recommend golden potatoes, however red skinned potatoes work equally well. Russets will work too, but the skin is thicker.
- Garlic - Roasted garlic is divine in Potatoes Au Gratin, however you can substitute with garlic powder or fresh garlic that gets cooked with the onion.
- Cheese - Pre-shredded cheese won't melt as nicely, so I recommend grating it from a block. Cheddar works great, but I actually prefer to use a cheddar-gruyere blend. You can use different cheeses like Jack as well.
- Make ahead directions: You can prepare this recipe a day ahead of time up until the point where the Potatoes Au Gratin goes into the oven. Cooking time might need to be extended if you take it straight out of the refrigerator.
Love cheesy potatoes? Me too! Here are some tasty favorites you can make.
- Loaded Potato Skins
- Loaded Baked Potato Soup
- Pressure Cooker (Instant Pot) Baked Potatoes - smother them with cheese!
- Cheddar Herb Sweet Potato Mash
- Twice Baked Ranch Potato Poppers
- Cheddar Bacon Ranch Roasted Potatoes
If you’ve made this or any other recipe on my site, let me know in the comment section how it turned out. I love hearing from my readers!
Potatoes Au Gratin
- 3 pounds golden potatoes (lightly scrubbed, skin on, and sliced thin, see note)
- 1 medium yellow onion (peeled and sliced thin)
- 4 tablespoons unsalted butter
- 4 tablespoons all-purpose flour
- 2 cups whole milk
- 4 cloves roasted garlic (smashed into paste)
- 1 teaspoon dry mustard
- 1/4 teaspoon nutmeg (freshly grated )
- 2 cups cheddar cheese (shredded (I used a cheddar gruyere blend))
- 1 teaspoon Kosher salt (or more, to taste)
- 1/2 teaspoon pepper ( freshly ground)
- Preheat oven to 400 degrees F.
- Wash potatoes and slice into thin slices. Soak in large bowl of cold water for at least an hour.
- Melt butter in a sauce pan and add sliced onion. Stir to coat in butter and then allow to cook, undisturbed, until the onion starts to brown. Add the flour and cook 2-3 minutes, stirring constantly to avoid burning. You want mixture to smell like a cooked pie crust. Add milk and whisk over medium heat until thick and bubbly. Remove from heat and stir in roasted garlic, dry mustard, nutmeg, and cheese until melted.
- Place potato slices upright in a greased casserole dish. Sprinkle with salt and pepper. Spoon cheese sauce over potatoes.
- Cover with greased lid or foil and bake 35 minutes, covered. Remove cover and bake an additional 20-30 minutes or until lightly browned and potatoes are cooked.
- A mandolin is the easiest way to get super thin sliced potatoes.
- The thinner your potatoes, the faster they will cook. If you do not slice with a mandolin, you may have to increase your cooking time. Likewise, if potatoes are not of uniform thickness, the thin slices will cook much faster than the thick slices.