I perfected my Cheesy Potato Au Gratin using three cheeses and one little trick that yields creamy layers and a perfectly golden top.

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I never set out to create the CHEESIEST au gratin potatoes but somehow I did, and everyone calls it Cheesy Potato Au Gratin. Thinly sliced Yukon Gold potatoes soak up a silky sauce built from three types of cheese, with Gruyere giving that nutty, almost smoky lift.

I’ve got a few dumb tricks that make the middle deadly creamy and the top impossibly golden, though sometimes I burn the edges cause I get distracted. It’s loud, it’s indulgent, and it makes guests suspiciously polite when they want seconds.

If you like cheese, this will ruin other potato sides for you.

Ingredients

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Starchy carbs and potassium; fills you up, soaks up creamy, cheesy flavors.
Nutty, melty Gruyere; adds protein and calcium, gives savory depth without being too sharp.
Bold, tangy cheddar; brings sharp flavor, color, higher fat and sodium.
Milk and cream make it silky and rich; add fat, calories and calcium.
Onion and garlic give aroma and sweet savor; low cal, add flavor depth.
Butter boosts richness and mouthfeel; helps sauté and bind flavors with fat.
Nutmeg warms subtly, Dijon brightens acidity; tiny amounts lift the whole dish.

Ingredient Quantities

2 1/2 to 3 lb russet or Yukon Gold potatoes, peeled and very thinly sliced (about 6 cups)

3 tablespoons unsalted butter, divided

1 medium yellow onion, thinly sliced

2 cloves garlic, minced

3 tablespoons all-purpose flour

1 1/2 cups whole milk

1 1/2 cups heavy cream

1 teaspoon Dijon mustard

1 teaspoon kosher salt

1/2 teaspoon freshly ground black pepper

1/4 teaspoon ground nutmeg

1 1/2 cups Gruyere cheese, grated

1 1/2 cups sharp cheddar, grated

1/2 cup freshly grated Parmesan cheese

1/2 cup extra grated sharp cheddar for topping (optional)

2 tablespoons panko breadcrumbs for topping (optional)

2 tablespoons chopped fresh chives or parsley for garnish (optional)

How to Make this

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1. Preheat oven to 375°F (190°C) and butter a 9×13 inch baking dish with a little of the butter. Peel and very thinly slice the potatoes (a mandoline is easiest) to about 1/8 inch thick, put them in a bowl and set aside.

2. Melt 1 tablespoon butter in a skillet over medium heat, add the thinly sliced onion and cook until soft and starting to brown, 6 to 8 minutes. Add the minced garlic for 30 seconds, then take the pan off heat and set the onion and garlic aside.

3. In the same skillet melt the remaining butter, sprinkle in the 3 tablespoons flour and whisk to make a roux, cook 1 to 2 minutes until lightly golden. Slowly whisk in the 1 1/2 cups whole milk and 1 1/2 cups heavy cream, bring to a gentle simmer and cook until the sauce thickens, about 3 to 5 minutes.

4. Stir in 1 teaspoon Dijon mustard, 1 teaspoon kosher salt, 1/2 teaspoon black pepper and 1/4 teaspoon ground nutmeg, taste and adjust seasoning if needed.

5. Remove the sauce from heat and stir in the grated cheeses: 1 1/2 cups Gruyere, 1 1/2 cups sharp cheddar and 1/2 cup Parmesan until melted and smooth. Keep a little cheese back if you want extra for the top.

6. Layer half the potato slices in the prepared dish, overlap them slightly, sprinkle half the sautéed onion over the potatoes, pour half the cheese sauce evenly. Repeat with the remaining potatoes, onions and sauce so everything is used.

7. Cover the dish tightly with foil and bake 30 to 35 minutes, then remove foil and continue baking 15 to 25 minutes until the potatoes are tender when pierced with a knife and the top is bubbling and golden.

8. If using the optional topping mix the 1/2 cup extra grated sharp cheddar with 2 tablespoons panko breadcrumbs and scatter over the gratin before the final bake, or sprinkle them on after removing the foil and return to oven until browned. You can toss the panko with a little melted butter for extra crisp, if you want.

9. Let the gratin rest 10 to 15 minutes so it sets, then garnish with 2 tablespoons chopped fresh chives or parsley and serve.

Equipment Needed

1. 9×13 inch baking dish (butter it first)
2. Mandoline (easiest) or a sharp chef’s knife and cutting board
3. Large mixing bowl for the sliced potatoes
4. 10 to 12 inch skillet for sautéeing and making the sauce
5. Whisk for the roux and cream sauce
6. Wooden spoon or heatproof spatula for stirring
7. Box grater or microplane for the cheeses and nutmeg
8. Measuring cups and spoons
9. Aluminum foil and oven mitts for baking and handling hot dish

FAQ

How thin should I slice the potatoes and what tool should I use? Slice them very thin, about 1/8 inch if you can. A mandoline makes it fast and even, but a sharp knife works fine if you take your time. Thinner slices cook more evenly, but don’t make them paper thin or they’ll fall apart.

My gratin turned out watery how do I avoid that? Don’t over-soak the potatoes. A quick rinse to remove surface starch is okay, then pat them completely dry. Make sure the sauce is bubbling when you pour it over the potatoes, and cover the dish for most of the bake time so the liquid gets absorbed. If it’s still loose at the end, uncover and bake longer to evaporate moisture.

Can I swap the cheeses or use lower fat milk? Yes kinda. Gruyere and sharp cheddar give the best flavor, but you can use fontina, Swiss or a good melting mozzarella if needed. Whole milk and heavy cream give the creamy texture; you could use half-and-half or a mix of milk and cream to cut fat but the sauce will be less rich.

Can I make this ahead or freeze it? You can assemble ahead and refrigerate up to 24 hours before baking. For freezing, assemble but don’t bake, wrap tightly and freeze up to 1 month. Thaw in the fridge overnight then bake. Texture might change a little after freezing, so results are best fresh or refrigerated short term.

How do I know when it’s done? Bake at about 350 F until potatoes are tender and sauce is bubbly, usually 55 to 75 minutes depending on thickness and dish size. Stick a knife or skewer in the center it should slide through easily. If the top isn’t browned, remove foil and bake a few more minutes until golden.

What’s the best way to store and reheat leftovers? Cool then refrigerate for up to 4 days. Reheat in a 350 F oven until warmed through, about 20 to 30 minutes, so it stays creamy and not soggy. Microwaving works for a quick fix but you’ll lose some texture and the top won’t be crisp.

Creamy & Cheesy Au Gratin Potatoes Recipe Substitutions and Variations

Potatoes: If you don’t have russets or Yukon Gold try red potatoes or fingerlings for firmer slices, or go bold with sweet potatoes for a sweeter, earthier dish.
Milk + Heavy Cream: Replace both with 3 cups half-and-half for an easy one-bowl swap, or use 2 cups whole milk plus 1 cup evaporated milk; for dairy-free use full-fat canned coconut milk or cashew cream.
Gruyere and Sharp Cheddar: Swap Gruyere with Swiss, Emmental or ComtĂ© (Fontina melts well too). For sharp cheddar try aged white cheddar, Colby, or Monterey Jack for a milder melt; Pecorino Romano or Asiago work for Parmesan.
All-purpose Flour: Use 2 tablespoons cornstarch mixed with cold water as a gluten-free thickener, or a 1:1 gluten-free flour blend, or potato starch for a glossy sauce.

Pro Tips

1. Slice the potatoes as thin and even as you can, it makes the whole dish cook evenly and not end up with some crunchy bits while other slices are mush, and if you use a mandoline wear the safety guard or a cut resistant glove cause they will bite you.

2. Grate your own cheese, dont use the pre-shredded stuff, it melts way better and gives a silkier sauce; add the cheese off the heat and stir gently so it doesn’t get grainy or oily.

3. Season between layers instead of dumping all the salt at the end, that way every bite tastes good, and dont pack the layers too tight or they’ll take forever to cook through.

4. Start covered so the potatoes steam and become tender then uncover near the end to brown the top, if the top is getting too dark move the dish down a rack or tent foil loosely for a few minutes.

5. For a real crunchy top toss panko with a little melted butter before sprinkling, or crisp the crumbs in a skillet first and add them right before serving so they stay crunchy and dont turn soggy while it rests.