This dreamy side dish is everything you love about French onion soup baked into fluffy mashed potatoes. Caramelized onions, melty cheese, and creamy mashed potatoes are swirled together, then baked until golden and bubbling on top. It takes the comfort of mashed potatoes and elevates it with a rich, savory twist.

Perfect for holidays or special family dinners, these twice baked mashed potatoes are both nostalgic and indulgent. Every bite brings that sweet onion depth and cheesy finish that turns a classic side into the highlight of the table.

Why You’ll Love This Twice Baked French Onion Mashed Potatoes

If you’re a fan of layered flavors, this is your kind of side dish. The onions are slow-cooked until deeply golden and jammy, infusing the mashed potatoes with an umami boost that’s hard to resist. Gruyère adds nuttiness and richness, while baking it twice gives you a warm, crusty top and ultra-creamy center.

This dish pairs with everything from roasted chicken to prime rib, but it also shines on a vegetarian spread. It’s cozy without being too heavy and makes excellent use of pantry ingredients you probably already have.

What Kind of Potatoes Should I Use?

The best potatoes for mashed are those with high starch content. Russet potatoes are ideal for this recipe since they create a fluffy mash that soaks up all the flavor from the caramelized onions and cheese. Yukon Gold potatoes are another great choice if you want a buttery taste with a creamier texture. Whatever you choose, peel and cube them evenly so they cook uniformly and mash without lumps.

Ingredients for the Twice Baked French Onion Mashed Potatoes

This recipe is simple but layered with flavor. The ingredient list balances basics like potatoes and butter with indulgent additions that make the dish unforgettable.

Russet potatoes: These give the mash its fluffy base and soak up all the flavor.
Yellow onions: Slowly caramelized, they bring the French onion character.
Butter: Adds creaminess and richness to the mashed base.

Heavy cream: For smooth, luscious texture.
Gruyère cheese: Classic for French onion recipes, it melts beautifully and adds deep savory notes.
Sour cream: Gives a tangy edge that balances the richness.

Salt: Essential for enhancing every element.
Black pepper: Adds warmth and slight bite.
Fresh thyme (optional): A hint of herbal flavor lifts everything.

Twice Baked French Onion Mashed Potatoes (1)

How To Make the Twice Baked French Onion Mashed Potatoes

Step 1: Caramelize the Onions

In a large skillet, melt butter over medium heat. Add sliced yellow onions and cook slowly, stirring often, for about 30 to 40 minutes until deep golden brown and jammy. Don’t rush this step; the richer the color, the more flavor they develop.

Step 2: Boil and Mash the Potatoes

Peel and cube the russet potatoes. Boil in salted water until fork tender, then drain. Mash with butter, heavy cream, sour cream, salt, and pepper until smooth.

Step 3: Mix in Caramelized Onions and Cheese

Fold the caramelized onions into the mashed potatoes, reserving a few tablespoons for topping. Stir in most of the Gruyère cheese and a sprinkle of fresh thyme if using.

Step 4: Transfer and Bake

Spoon the mixture into a greased baking dish. Top with the remaining onions and cheese. Bake at 375°F for 20 to 25 minutes, until the top is golden and bubbly.

Step 5: Serve Hot

Let it rest a few minutes before serving so the flavors meld together and it sets slightly for perfect scooping.

How to Serve and Store Twice Baked French Onion Mashed Potatoes

This recipe serves 6 to 8 people generously, making it ideal for a gathering or holiday meal. It holds its own on any table but also plays beautifully with meaty mains or a hearty vegetarian spread.

Leftovers can be stored in an airtight container in the refrigerator for up to 4 days. To reheat, bake covered at 350°F until warmed through, or microwave in short bursts with a splash of cream to revive the texture.

What to Serve With Twice Baked French Onion Mashed Potatoes?

Roast Chicken with Herbed Skin

The juicy meat and crisp skin pair wonderfully with the creamy potato base.

Garlic Butter Steak Bites

The rich sear of steak bites makes the onion mash a perfect counter.

Vegetarian Mushroom Gravy

Spoon some over the potatoes for an earthy, umami-forward dish.

BBQ Chicken Pizza

Yes, pizza. It’s indulgent, and the sweet-savory barbecue sauce plays off the onion perfectly.

Simple Green Beans with Lemon

Fresh, snappy green beans lighten up the meal and cut through the richness.

Creamy Mushroom Sauce for Steak

A double-down on creamy comfort with this luxurious pairing.

Warm Brussels Sprout Salad

Add some crunch and tang to the table with crispy roasted sprouts and vinaigrette.

Want More Side Dish Ideas?

If you’re loving the comfort of these potatoes, you might also enjoy:

Easy Chicken with Zucchini Corn Garlic Sauce

Save This Recipe For Later

📌 Save this recipe to your Pinterest board so you can come back to it any time.

Let me know in the comments how yours turned out! Did you stick to Gruyère or mix in something bold like smoked gouda? Did you add a crispy topping?

Explore beautifully curated comfort food dishes on Luna Meals on Pinterest and discover your next cozy favorite.

Conclusion

Twice Baked French Onion Mashed Potatoes are the kind of recipe that impresses guests but also feels like home. With just a few pantry staples and some patience while those onions caramelize, you get a dish that’s rich, creamy, and layered with flavor. Whether it’s a holiday table or just a Tuesday, this is the side dish that makes everything feel special.

Twice Baked French Onion Mashed Potatoes

Why You’ll Love This Twice Baked French Onion Mashed Potatoes

What Kind of Potatoes Should I Use?

Ingredients for the Twice Baked French Onion Mashed Potatoes