These Twice-Baked French Onion Mashed Potatoes are rich, creamy, and packed with flavor. The potatoes are whipped with butter, cream, and cheese, then baked with more melty Gruyere cheese, and finished with a generous layer of sweet, deeply caramelized onions just before serving. It’s like French onion soup meets mashed potatoes! Craving something even cheesier and loaded with hashbrowns? Check out my French Onion Funeral Potatoes, too!
Ingredients & Substitutions
- Potatoes: I use peeled red potatoes in this recipe because they have a naturally creamy texture and mild flavor that’s perfect for mashed potatoes. Peeling them makes the mash extra smooth and velvety. That said, I love using red potatoes with the skins on for my Skins On Mashed Potatoes, too! Don’t have red potatoes? You can also use Yukon Gold for a super creamy texture or Russet potatoes for a fluffier, lighter texture.
- Butter: I used unsalted butter in this recipe so you can control the saltiness better. Some is used to caramelize the onions, and then I use more to add with the cream to make the mashed potatoes extra creamy and smooth.
- Onions: This recipe calls for yellow onions, which caramelize beautifully and have a nice balance of sweetness and savory flavor. If you don’t have yellow onions, you can also use white onions or sweet onions like Vidalia.
- Heavy Whipping Cream: The heavy whipping cream makes the mashed potatoes extra rich and creamy. If you want a lighter option, you can substitute with half-and-half or even whole milk, but the texture won’t be quite as thick and indulgent.
- Cheese: I use Gruyère cheese because it melts beautifully and has a rich, nutty flavor that pairs perfectly with the caramelized onions. If you don’t have Gruyère, you can also use Swiss, mozzarella, or cheddar cheese. I added half of the cheese to the mashed potatoes, and then used the rest to bake on top of the potatoes.
Do I Have To Peel The Potatoes?
For the smoothest texture, peeling the potatoes is best. But if you like a more rustic mash, you can leave the skins on, just wash them well. I love skins-on mashed potatoes!
Can I Use Pre-Made Or Store-Bought Mashed Potatoes For Twice-Baked French Onion Mashed Potatoes?
Yes, you can definitely use pre-made mashed potatoes to save time! Whether homemade or store-bought, just spread them in your baking dish, top with Gruyere cheese, and bake until hot and bubbly. Then finish with the caramelized onions on top before serving. But if you have the time, making the mashed potatoes from scratch is worth it! They are extra creamy and full of flavor!
Can I Make Twice-Baked French Onion Mashed Potatoes Ahead Of Time?
Yes! You can assemble the potatoes (without the onions) up to 1 day in advance. Cover and refrigerate. For best results, add the cheese topping just before baking so it melts and browns evenly, but adding it ahead is fine, too. You can also caramelize the onions a day ahead. Just store them in the refrigerator and rewarm before spooning over the baked mashed potatoes.
Why Add Caramelized Onions After Baking?
We tested folding the caramelized onions into the mashed potatoes before baking, but they ended up getting lost in the mix. The potatoes were creamy, but the signature French onion flavor just disappeared. And that is not what I was going for! Adding the onions on top after baking keeps them front and center, sweet, golden, and full of flavor, just like the best part of French onion soup. This way, every bite gets that rich, caramelized onion goodness!
Can I Use a Different Baking Dish?
Yes! If you don’t have a 10-inch oven-safe skillet, you can bake these potatoes in an 8×8-inch or 9×9-inch square dish. (The recipe made about 6 cups of mashed potatoes.) A 2.5-quart round casserole dish or a 7×11-inch rectangular baking dish would also work. Just keep in mind that the thickness of the potato layer may vary slightly depending on the dish you choose, so keep an eye on the baking time. You’re looking for the cheese to be fully melted and golden on top.
Can I Skip the Baking Step and Just Make Mashed Potatoes with Caramelized Onions?
Yes! If you want to save time or prefer a creamier texture without the baked cheesy top, you can skip the oven step. Just mash the potatoes as directed, stir in all of the Gruyère cheese (instead of dividing it), and top with the caramelized onions. The flavors will still be rich and delicious. But you might miss the golden, bubbly crust!
How To Store and Reheat Twice-Baked French Onion Mashed Potatoes
To store the twice-baked French onion mashed potatoes, first, let the potatoes cool completely. Then, cover tightly with aluminum foil or transfer to an airtight container. Store in the refrigerator for up to 3–4 days. To reheat, for best results, reheat in the oven. Cover the dish with foil and bake at 350°F for about 20–25 minutes, or until warmed through. You can also reheat individual portions in the microwave. If the potatoes seem a little thick after chilling, stir in a splash of cream or milk before reheating to bring back that creamy texture.
Can I Freeze French Onion Mashed Potatoes?
Yes, you can freeze French Onion Mashed Potatoes! Let them cool completely, then transfer to a freezer-safe container or wrap tightly with aluminum foil and plastic wrap. Freeze for up to 2 months. When ready to serve, thaw in the refrigerator overnight. Reheat covered in a 350°F oven until heated through. Add a splash of cream or milk if needed to bring back that creamy texture.
Twice Baked French Onion Mashed Potatoes
Ingredients
Caramelized Onions
- 3 large yellow onions (about 2 pounds total), sliced into half moons
- 2 tablespoons extra virgin olive oil
- 1 tablespoon unsalted butter
- ½ teaspoon kosher salt
- 1-2 tablespoons water or broth, for deglazing
Potatoes
- 3 pounds red potatoes, washed, peeled, quartered
- ½ cup (1 stick / 113 g) unsalted butter
- ½ cup (119 g) heavy whipping cream
- 1 teaspoon kosher salt
- ½ teaspoon black pepper
- 1 cup (113 g) Gruyere cheese, shredded, divided
- parsley, chopped for garnish
Instructions
Caramelized Onions
- To a large skillet over medium heat, add the olive oil and butter. Once the oil is shimmering and the butter is melted, stir to combine.
- Add the sliced onions and toss them to coat evenly. Spread them out into an even layer across the skillet.
- Sprinkle the kosher salt over the onions. This helps draw out moisture, which is essential for even caramelization.
- Reduce heat to medium-low. Let the onions cook, stirring them every 5–10 minutes. You want to allow them time to rest against the pan so they brown slowly and evenly.
- Continue cooking, stirring occasionally, for 60-70 minutes total. The onions should turn a deep golden brown, become very soft, and almost jammy in texture. (If at any point the onions look like they’re browning too fast or burning on the bottom, reduce the heat slightly and add a splash of water or broth to deglaze and scrape up any browned bits.)
Potatoes
- While the onions are cooking, place the potatoes in a large pot and cover them with cold water.
- Set the pot over high heat and cover with a lid. Let the water come to a full boil.
- Once boiling, remove the lid and reduce the heat to medium-high. Simmer the potatoes until they’re fork-tender, about 20–25 minutes.
- While the potatoes are boiling, preheat the oven to 425°F (220°C). Lightly grease a 10-inch oven-safe skillet* and set aside.
- Drain the cooked potatoes and return them to the pot. Use a potato masher to mash lightly.
- Add the butter, heavy whipping cream, salt, black pepper, and half of the shredded Gruyère cheese. Continue mashing and stirring until the mixture is smooth and creamy.
- Spoon the mashed potatoes into the prepared baking dish, spreading them out evenly.
- Sprinkle the remaining Gruyère cheese evenly over the top.
- Bake for 15–20 minutes, or until the cheese is fully melted and golden brown on top.
- Remove from the oven. Top with the warm caramelized onions.
- Garnish with chopped parsley and serve warm.
Notes
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What the Test Kitchen had to say about this recipe:
Autumn
This might be one of my new favorite side dishes! It is so creamy and flavorful! And, the caramelized onions make the potatoes extra special!
Elizabeth
I love twice baked potatoes, but twice baked mashed potatoes? Yes, please! I would say they are twice as good as regular mashed potatoes! I love the cheese on top and the caramelized onions in every single bite!
Stephanie
I love how rich and cheesy these potatoes are! And, the caramelized onions are so good.
Bella
I wasn't sure about twice baked mashed potatoes, but I get it now! These are wonderful, especially with the cheese baked on top!
Excellent dish for a favorfil change in potatoes