These flavorful and creamy au gratin potatoes make a beautiful addition to any dinner table! Perfect for feeding a crowd at celebrations like Easter, Christmas, or Thanksgiving.
Nothing screams "delicious side" quite like a potato casserole. Today, we're making a cheesy version of scalloped potatoes (also known as potatoes au gratin!)
scalloped vs au gratin potatoes:
Really the only difference between classic scalloped potatoes and potatoes au gratin is the addition of cheese. Scalloped potatoes are typically made cheese-less while potatoes au gratin feature some kind of grated cheese.
The two dishes are otherwise identical in the ingredients they use and their prep, with both featuring potatoes and a béchamel sauce.
What is a béchamel sauce?
Béchamel sauce is essentially a milk sauce that's thickened with a "roux".
What's a roux - you may or may not ask? A roux is a mixture of equal parts flour and butter (so a 1:1 ratio) that is lightly toasted. Liquid is added to the roux and everything is cooked together. The roux is essential for thickening the sauce.
This recipe features a cheesy béchamel sauce (very similar to queso cheese dip)!
potatoes au gratin ingredients:
• potatoes: one of the best things about this recipe is that you could use basically any potato you like. I like to stick to using either yellow or white potatoes just because that's what I usually keep on hand. You could also make potatoes au gratin with red or russet potatoes.
• butter: for cooking the onions and garlic, annnnnd as the main fat for the roux.
• onion + garlic: you'll find these in most classic potatoes au gratin recipes. They add ahhhhh-mazing flavor!
• flour: helps thicken the sauce
• milk: as the main body for the sauce. Some people like to add vegetable / chicken / beef stock to the béchamel sauce with the milk. I don't really keep stock on hand, and I crave potatoes au gratin every other day ..... sooooo we're sticking with an all milk béchamel. You really can't tell much of a difference anyways.
• salt + black pepper: you can also add some other herbs and spices if you like. Some popular choices include ground nutmeg, thyme, rosemary, or oregano.
• cheese: I included cheddar cheese in the sauce and Pecorino Romano on top for a crispy finish!
how to make potatoes au gratin:
1. Prep the potatoes: Peel, slice and wash the potatoes. Set aside to prep the béchamel sauce.
2. Melt butter and add in onions. Cook until softened, then add in garlic to toast until fragrant.
3. Mix in flour. Cook for about 1 minute to toast the flour and cook out the raw taste.
4. Gradually mix in milk until smooth and combined. Mix in salt and pepper. Cook the sauce until it boils and thickens enough to coat the back of a spoon.
5. Add in grated cheddar. Mix together until the cheese is melted and well combined.
6. Layer your casserole! Pour in about ¼ of the sauce, and arrange about ⅓ of the sliced potatoes overtop. Continue layering until everything is stacked (finishing with the remaining ¼ of the sauce on top).
7. Top with cheese & bake. Bake covered until fork tender, then uncover and bake until golden brown on top.
8. Rest & serve. Let the baked potatoes sit for 15 to 20 minutes to allow the sauce to set up before serving!
Tips for making potatoes au gratin:
• Gradually whisk milk into the roux. It can clump if the milk is added in too quickly at the beginning. Start off super slow when adding in the milk, whisking well before adding any more. Once you've added about half of the milk and it's all smooth, you can add the rest in all at once without issue!
• Use freshly grated cheese! I always say this and will never stop saying it: freshly. grate. your. cheese! Pre-shredded mixes almost always have a coating on them to help them last and keep from sticking together - which ultimately means it won't melt as smoothly and creamily! Trust me, NO ONE hates grating cheese as much as me, but it's well worth the results!
Speaking of cheese...
• Take your pot off the heat before adding the grated cheddar. Overcooked cheese will clump up, so the best way to avoid a grainy béchamel sauce is to add the cheese into it off the heat. The béchamel should still be hot, but don't continue cooking it once the cheese is added.
• Bake well! Is there anything worse than a beautiful looking potato casserole that's under-baked and raw? Well, probably, but there's nothing worse than uncooked potatoes in the potato making world! The bake time for this recipe may seem like a lot, but it's MORE than necessary to get perfectly softened potatoes.
• Rest your dish before serving. If you try cutting into the potatoes au gratin straight from the oven, the sauce is going to be QUITE watery. Letting it sit for 15 to 20 minutes after baking gives the sauce a chance to firm up and absorb into the potatoes.
potatoes au gratin make ahead and reheating leftovers:
Big celebrations and holidays call for as much make ahead as possible and leftovers are almost ALWAYS to be expected.
To make these potatoes ahead, cook the béchamel sauce, and layer your potatoes. Cover the unbaked casserole, and keep stored in your fridge for up to 3 days before you're ready to bake and serve them!
Let the layered potatoes sit out at room temperature for 30 minutes to warm up before baking as instructed below!
To store leftovers, let the potatoes cool completely to room temperature, cover with plastic wrap, and keep in the fridge for up to 3 days.
To reheat leftovers, set the potatoes out at room temperature for 1 hour to warm slightly. Cover with aluminum foil, and bake in a preheated 350°F oven for 15 to 20 minutes, or until heated through.
Check out these other side recipes!
Cheesy Scalloped Potatoes (Potatoes au Gratin Recipe)
- 3 pounds Yukon gold or white potatoes, about 10 medium sized potatoes
- 5 tablespoons unsalted butter
- 1 medium red or yellow onion, peeled and finely diced
- 5 cloves garlic, peeled and finely minced
- ⅓ cup all-purpose flour
- 3 cups milk
- 1 & ½ teaspoons salt
- ¼ teaspoon black pepper
- 1 cup medium cheddar cheese, freshly shredded *see notes
- ½ cup Parmesan or Pecorino Romano cheese, finely grated
- Preheat your oven to 350°F.
- Prep the potatoes: Peel your potatoes and cut into slices that are about ⅛th of an inch thick. Rinse well to remove any dirt or starch, and drain. Set aside.
- Prep the béchamel sauce: Heat butter in a medium sized saucepot placed over a stove burner set to medium heat until melted and sizzling.
- Add your onions and cook until soft and translucent (about 2 minutes). Add the minced garlic, and cook for another 30 seconds to 1 minute, or until fragrant.
- Sprinkle flour over the onion / garlic mixture. Cook, stirring constantly, for 1 minute to toast the flour and remove any raw taste.
- Gradually pour the milk into the pot, whisking well after each addition. Take your time here and work slowly to prevent clumps. Sprinkle in salt and black pepper.
- Cook the mixture, whisking constantly, until it boils and thickens enough to coat the back of a spoon. This should take about 5 to 10 minutes.
- Turn off the heat and take the pot off the stove. While the mixture is still hot, add in your grated cheddar, and whisk until the cheese is dissolved and the mixture is smooth.
- Assemble! Pour about ¼ of the cheesy béchamel sauce into a 9x13 inch baking dish. Arrange ⅓ of the sliced potatoes in an even layer over the sauce. Continue layering sauce and potatoes until they're all stacked together. Sprinkle Parmesan or Pecorino Romano cheese over top.
- Cover the layered potatoes tightly with aluminum foil, and bake in the center of your preheated 350°F oven for 45 to 60 minutes covered, or until fork tender. Uncover, and cook for another 15 to 20 minutes, or until golden brown on top. If you'd like an extra golden top, broil for 1 to 2 minutes on high.
- Take the cooked potatoes out of the oven and set aside to rest for 15 to 20 minutes to allow the sauce to firm up and set before serving!