Name: French Onion Scalloped Potatoes Recipe
Prep time: 1 h
Cook time: 1 h
Total time: 2 h
Cuisine: French
Ingredients: 4 sweet onions, thinly sliced; 4 tablespoons unsalted butter; Kosher salt and pepper, to taste; ½ teaspoon dried thyme; 3 pounds russet potatoes, peeled; 4 tablespoons unsalted butter; 4 tablespoons all-purpose flour; 3 ½ cups milk; Kosher salt and pepper, to taste; ¼ teaspoon freshly grated nutmeg; 12 ounces freshly grated gruyere cheese (divided); ⅓ cup seasoned bread crumbs

Jump to Recipe· 4.5 from 284 reviews

If you love the golden, rich flavors of caramelized onions and the comforting creaminess of potatoes, get ready to fall head over heels for this French Onion Scalloped Potatoes Recipe. It’s one of those dishes that feels like a warm hug on a plate—perfect for family dinners, holidays, or whenever you want to treat yourself to something a little fancy yet totally homey. I absolutely love how the sweet onions blend so beautifully with the cheesy sauce, making every bite melt in your mouth. Trust me, you’ll want to bookmark this one.

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Why You’ll Love This Recipe

Deep Caramelized Flavor: Those slow-cooked onions develop such a sweet, rich taste that elevates the whole dish.
Cheesy, Creamy Goodness: The gruyere-infused sauce is velvety and indulgent without being overly heavy.
Make-Ahead Friendly: You can prep it partly in advance, which I find so handy for busy days or entertaining.
Crowd-Pleasing Comfort Food: Perfect for large groups or holiday gatherings—it always disappears fast!

A close-up view of a baked dish in a white casserole with a crusty top layer of melted golden cheese mixed with darker brown toasted bits and sprinkled with small fresh green herb leaves. The cheese has a slightly bubbly texture with some browned edges, and there are thin, shredded orange pieces scattered on the surface. The casserole rests on a white marbled background. photo taken with an iphone --ar 2:3 --v 7 - French Onion Scalloped Potatoes, caramelized onion potato casserole, cheesy scalloped potatoes, onion and potato gratin, comfort food side dishes

Ingredients You’ll Need

I like to keep these ingredients straightforward, but quality matters—especially with the onions and cheese. Fresh sweet onions and a nice aged gruyere really make the difference.

Flat lay of thinly sliced sweet onions in soft translucent white and pale purple layers, whole russet potatoes with smooth light brown skins, fresh sprigs of dried thyme with tiny green leaves, a small pile of golden unsalted butter blocks, grated gruyere cheese showing pale yellow shreds with a slightly creamy texture, a neat mound of seasoned golden brown bread crumbs with crispy texture, and a tiny grating of fresh nutmeg with warm brown tones, all beautifully arranged in a natural, slightly overlapping pattern with varied shapes and textures, placed on white marbled surface, photo taken with an iphone --ar 2:3 --v 7 - French Onion Scalloped Potatoes, caramelized onion potato casserole, cheesy scalloped potatoes, onion and potato gratin, comfort food side dishes

Sweet onions: They caramelize beautifully, lending a natural sweetness that balances the cheesy richness.
Unsalted butter: Gives you control over seasoning and makes a luscious base for both the onions and the sauce.
Kosher salt and pepper: Simple seasoning that enhances every layer of flavor.
Dried thyme: Adds a subtle herbal note that complements the onions without overwhelming them.
Russet potatoes: Their starchy texture results in tender, creamy layers once baked.
All-purpose flour: Essential for thickening the sauce to that perfect scalloped consistency.
Milk: Use whole or 2% for best creaminess—this is the backbone of your sauce.
Freshly grated nutmeg: Just a pinch brings warmth and depth to the sauce.
Gruyere cheese: Melts into a dreamy, nutty finish that ties the whole dish together.
Seasoned bread crumbs: They add a lovely golden crunch on top—you don’t want to skip these!

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Note: You’ll find the complete list of ingredients, along with their exact measurements, in the printable recipe card at the bottom of this post.

Variations

I love how versatile this French Onion Scalloped Potatoes Recipe is. Once you get the basics down, you can tweak it to match your tastes or dietary needs—trust me, it still shines.

Make it vegetarian: Simply swap out chicken or beef broth (if ever used) for vegetable broth, or stick to just milk and butter—I’ve done this and it’s just as decadent!
Swap cheeses: If you don’t have gruyere, aged cheddar or fontina works well. I experimented once with smoked gouda and loved the smoky twist.
Herbal twist: Fresh rosemary or sage can replace thyme for a woodsy flavor. I add rosemary when it’s holiday time—it feels festive!
Low carb version: Try a blend of turnips and cauliflower with the same onion and cheese sauce. Not exactly the same texture, but still yummy and comforting.

How to Make French Onion Scalloped Potatoes Recipe

Step 1: Slowly Caramelize the Onions

Start by thinly slicing your sweet onions—this is key because uniform thin slices cook evenly and melt down beautifully. Heat butter in a skillet over medium heat, then toss in your onions with a hearty pinch of salt and pepper. Here’s where patience pays off! Stir occasionally for about 10 minutes until the onions soften, then lower the heat to medium-low and add your dried thyme. Now, stir often and let the onions cook slowly for 30 to 40 minutes until they’re golden, sticky, and caramelized. I’ve made the mistake of turning up the heat too fast before, which just burns them—so if they start to burn, always lower the heat or add a splash of water.

Step 2: Thinly Slice Your Potatoes

While the onions work their magic, slice your potatoes as thin as possible—ideally ⅛ inch or less. I love using a mandoline for this because it gives you perfect uniformity, which helps them cook evenly. If you slice them early, soak the slices briefly in ice water to prevent browning. Dry them well before layering to avoid excess moisture.

Step 3: Make the Creamy Gruyere Sauce

In a saucepan, melt butter over medium heat, then whisk in flour to form a roux. Let it cook 2 to 3 minutes until it’s golden and smells nutty—that’s your flavor foundation. Slowly add milk while whisking constantly to avoid lumps. Once smooth, stir in salt, pepper, and that magical pinch of freshly grated nutmeg. Lower heat and gradually melt in half the grated gruyere cheese, stirring until silky and combined. I always taste here and adjust seasoning before layering.

Step 4: Layer Your Dish

Grab a roomy baking dish and start layering: half of the sliced potatoes go in first, then half the cheesy sauce, half the caramelized onions, and half the remaining gruyere cheese. Repeat these layers, ending with cheese sauce, caramelized onions, and a generous sprinkle of seasoned bread crumbs. The crunchy topping adds such a wonderful texture contrast.

Step 5: Bake Until Perfectly Tender

Bake uncovered at 375°F for 45 to 60 minutes. The key sign you’re looking for? Tender potatoes you can easily pierce with a fork and a golden, bubbly top. If it browns too fast, tent it with foil—this trick saved me many times! Let it sit a bit before serving so it sets nicely.

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Pro Tips for Making French Onion Scalloped Potatoes Recipe

Onion Patience Pays Off: Don’t rush caramelizing—low and slow for deep flavor is totally worth the time.
Mandoline Magic: Using a mandoline ensures even potato slices—no uneven cooking or chewy bits.
Cheese Quality Matters: I once used pre-shredded cheese and it didn’t melt as smoothly; freshly grated gruyere is the way to go.
Watch Your Bake Time: If the top browns before potatoes are done, tent with foil—this keeps things perfect.

How to Serve French Onion Scalloped Potatoes Recipe

A white plate with a serving of scalloped potatoes layered about five thin layers deep, each layer showing soft, pale yellow potato slices with a slight creaminess between them. The top layer is golden brown with some crispy browned bits, giving a mix of creamy white and caramelized brown colors. Small bits of browned onions and melted cheese are scattered on and between the potato layers. A gold fork rests on the right side of the plate, beside the potato serving. The plate sits on a white marbled surface. Photo taken with an iphone --ar 2:3 --v 7 - French Onion Scalloped Potatoes, caramelized onion potato casserole, cheesy scalloped potatoes, onion and potato gratin, comfort food side dishes

Garnishes

I like to sprinkle fresh chopped parsley or chives on top just before serving—it adds a fresh, bright pop and contrasts beautifully with the rich layers beneath. A little flaky sea salt on top of the bread crumbs right after baking also takes this over the edge.

Side Dishes

This dish pairs fabulously with roasted chicken or a simple grilled steak. I often serve it alongside a crisp green salad to balance the richness. During holidays, it’s great next to glazed ham or even a roast beef.

Creative Ways to Present

For a special occasion, I’ve baked individual portions in ramekins—perfect for plating elegance. You can also swirl the bread crumb topping with a touch of Parmesan for a salted crunch upgrade. If you want to wow guests, consider layering with thin slices of caramelized shallots or even a sprinkle of crispy bacon bits.

Make Ahead and Storage

Storing Leftovers

I usually store any leftovers in an airtight container in the fridge for up to 3 days. When covered properly, the flavors actually deepen overnight—making for an even tastier next-day meal.

Freezing

I’ve frozen this dish once after baking and reheating, but I recommend freezing it before baking for better texture. Just assemble in a freezer-safe dish, cover tightly, and thaw overnight in the fridge before baking as usual.

Reheating

To reheat, I cover the dish loosely with foil and bake at 350°F until warmed through, about 20-30 minutes. This helps keep the top from over-browning while the insides get hot again without drying out.

FAQs

Can I make French Onion Scalloped Potatoes Recipe ahead of time?

Absolutely! You can caramelize the onions and slice the potatoes a day ahead. You can also assemble the casserole up to a day before baking; just cover it tightly and keep it refrigerated. When ready, bake as directed, adding a little extra time if chilled.
What type of potatoes works best for this recipe?

Russet potatoes are my go-to because their higher starch content creates creamy, soft layers once baked. Yukon golds can work too but may slightly change the texture.
Can I use other cheeses besides gruyere?

Yes! Gruyere adds a nutty, slightly sweet flavor, but you can substitute aged cheddar, fontina, or even a mix of mozzarella and parmesan for different twists on the texture and taste.
How do I prevent the potatoes from browning before baking?

After slicing, keep your potato slices submerged in cold water or ice water. This keeps them from oxidizing and turning brown. Just make sure to dry them well before layering into the dish.
Can I make this recipe dairy-free or vegan?

It would need some swaps: use plant-based butter and milk alternatives, and a vegan cheese substitute that melts well. Keep in mind the flavor and texture will differ from the classic version, but it can still be delicious!

Final Thoughts

Making this French Onion Scalloped Potatoes Recipe feels like a little luxury in my kitchen every time I prepare it. It’s an elegant spin on traditional scalloped potatoes with that caramelized onion magic that just can’t be beat. Whether you’re cooking for friends, family, or just treating yourself, I hope you’ll enjoy this one as much as I do. Give it a try—you might find it becoming your go-to comfort side dish or even the star of your next dinner!