Gruyere potatoes au gratin is a cheesy potato side dish that's perfect for your next holiday meal. Thin sliced potatoes are baked in a creamy herb sauce with melty gruyere cheese.
Gruyere potatoes au gratin is the ultimate comfort food side dish. Made with sliced potatoes, freshly shredded gruyere cheese, and a creamy herb sauce, it's sure to be a new family favorite.
Serve potatoes au gratin at your next family dinner, Easter, Christmas, or Thanksgiving. This recipe is easy to double or half, and can be made ahead and reheated the next day.
Ingredients and substitutions
- Potatoes - I recommend russet potatoes or yukon gold potatoes for this recipe. They're both easy to find at your local grocer and available year round.
- Onion & garlic - Add flavor to the casserole. I don't recommend omitting either of these ingredients.
- Butter - Unsalted butter can be substituted with salted butter if desired. I'd recommend reducing the listed salt by ¼ teaspoon.
- Flour - Mixed with the butter to make a roux, which thickens the cream sauce.
- Chicken broth - Adds flavor to the cream sauce. If using a low sodium broth, you may want to add a little extra seasoning to the sauce to make up for the lost flavor.
- Milk - I recommend using whole milk for best flavor and a thick, creamy texture. Lower fat milks can work but sauce will be thinner and has a higher chance of breaking in the oven.
- Seasoning - Salt, pepper, and thyme add flavor to the sauce. Thyme can be substituted with dried rosemary, oregano, or dill (like in my dill scalloped potatoes recipe).
- Gruyere cheese - Gruyere has a salty, nutty flavor that makes a great alternative to the standard cheddar that's used so often in casseroles. If you can't find gruyere, swiss cheese has a similar, slightly milder flavor. Cheddar cheese and monterey jack are also good substitutes. No matter what cheese you choose, I highly recommend freshly grating your own cheese from the block. Pre-shredded cheeses are often coated in anti-clumping powders that become grainy when melted.
Tips and tricks
Use a mandoline - My secret to perfectly sliced potatoes? Use a mandoline slicer, like this version on Amazon: mandoline slicer. I recommend setting it to ⅛" to ensure your casserole cooks through within the times listed in the recipe card.
Don't have a mandoline? - Many times your food processor will have an attachment to slice vegetables. Check the sides of your box cheese grater - one side may have a vegetable slicer. If all else fails, carefully slice your potatoes using a chef's knife. This option is the most time consuming.
Cook the sauce until it thickens - It may take several minutes for your sauce base to thicken on the stove top. If you've doubled this recipe to make two large casseroles, it will take even longer. Be patient, whisk occasionally, and it will slowly thicken. Your sauce is ready when it thickly coats the back of a spoon.
Frequently asked questions
Scalloped potatoes are not made with cheese, while potatoes au gratin are made with cheese. Otherwise, they're very similar dishes. The term scalloped potatoes is often used to describe both dishes, whether cheese is present or not.
There are a few reasons why a cream sauce can curdle. Most often, heat is the culprit. If the sauce is heated too high and for too long, it can cause the sauce to separate. If there's not enough fat in the sauce, like if you've used skim milk instead of whole milk, this can also cause it to separate.
Reduce the heat, then add a splash of heavy cream or a cube of butter to your sauce and stir to combine.
Yes. Potatoes au gratin can be assembled a day ahead and stored in the refrigerator overnight before baking. Cover your casserole dish with plastic wrap, pressing down to keep out as much air as possible. Exposed potatoes may discolor slightly overnight.
While your oven is preheating, bring the casserole to room temperature on the counter top, then bake as directed in the recipe card.
Yes. To reheat an entire baked casserole, preheat your oven to 350 degrees Fahrenheit while your casserole comes to room temperature on the counter top. Cover and bake for about 30 minutes or until heated through in the center.
Leftover potatoes au gratin will keep for about 4 days in a tightly sealed container in the refrigerator.
Gruyere Potatoes Au Gratin
- 3 pounds russet potatoes, or yukon gold
- 1 small onion, diced
- 4 cloves garlic, minced
- ¼ cup unsalted butter
- ¼ cup all-purpose flour
- 8 ounces chicken broth
- 16 ounces whole milk
- 1 ½ teaspoons salt
- ¾ teaspoon pepper
- ½ teaspoon dried thyme
- 2 cups freshly shredded gruyere cheese
- Preheat oven to 350 degrees Fahrenheit. Lightly grease a 9x13 casserole dish and set aside.
- Peel potatoes, rinse, and slice to ⅛" thickness. I recommend using a mandoline slicer if you have one available.
- In a saucepan over medium heat, add butter. Once melted, add onions and cook until they begin to brown and turn translucent, about 4-5 minutes. Add garlic and cook an additional 30 seconds. Add flour and stir to coat and create a paste. Cook for one minute.
- Whisk in broth and milk. Continue whisking until no lumps remain. Cook sauce for another 3-4 minutes, or until sauce thickly coats the back of a spoon. Remove from heat. Add salt, pepper, and thyme, stirring to incorporate.
- In prepared 9x13 pan, arrange ¼ of sliced potatoes in the bottom of the dish, overlapping slightly. Pour ¼ of sauce over potatoes. Repeat once more, adding another layer of potatoes and sauce. Next, add half of shredded gruyere cheese in an even layer. Add two more layers of potatoes and sauce (for a total of four layers each of potato and sauce), and top with remaining shredded cheese.
- Cover casserole with foil and bake for 45 minutes. Uncover and bake an additional 15-20 minutes, or until potatoes can easily be pierced through with a fork in the center of the casserole. The thicker your potatoes are sliced, the longer it will take for them to cook through.
- I recommend freshly shredding cheese from a block instead of using pre-shredded bagged cheese, which is often coated in an anti-clumping powder that becomes grainy when melted.
- Leftover casserole will keep for up to 4 days in a sealed container in the refrigerator.
- Casserole can be assembled ahead and stored in the refrigerator overnight before baking. Cover potatoes with plastic wrap, pressing down to keep out as much air as possible. Exposed potatoes may discolor slightly overnight. While oven is preheating, bring casserole to room temperature on the counter top, then bake as directed above.
- Casserole can be baked, cooled, and stored in the refrigerator overnight. To reheat entire baked casserole, bake, covered, at 350 degrees for 30 minutes, or until heated through in the middle.