Name: Twice Baked French Onion Mashed Potatoes
Prep time: 50 min
Cook time: 25 min
Total time: 1 h 15 min
Cuisine: American / French Fusion
Ingredients: 3 lbs Yukon Gold potatoes; 2 tablespoons olive oil; 2 large yellow onions, thinly sliced; 1–2 garlic cloves, minced (optional); 4 tablespoons butter; 1/2 cup heavy cream (warm); 1 teaspoon salt; 1/2 teaspoon black pepper; 1 cup shredded Gruyère cheese (divided); Fresh thyme or parsley, chopped (optional garnish)

I have a serious weakness for French onion anything, and this Twice Baked French Onion Mashed Potatoes recipe is my newest obsession. It takes everything I love about the classic soup—those deeply caramelized onions, buttery richness, and melty cheese—and layers it into a warm, creamy mashed potato bake. The result is a dish that feels like comfort food royalty, perfect for cozy dinners or the holiday table.

The first time I made this, it was meant to be a side dish. But the moment it came out of the oven, golden and bubbling with sweet onions on top, I knew it was going to steal the spotlight. It’s one of those recipes that makes people ask for seconds and then the recipe itself. Whether you’re planning Thanksgiving dinner or just need a new way to level up your mashed potatoes, this one’s a must-try.

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

This dish takes a familiar favorite and transforms it into something new and exciting. The creamy mashed potatoes form a luxurious base, and the addition of caramelized onions adds a deep, savory sweetness that makes every bite feel indulgent. The “twice baked” part? That extra step brings a lovely golden top and melds the flavors together in a way that’s impossible to resist.

If you’re someone who loves dishes that feel rich without being overly complicated, this one hits the mark. It’s also make-ahead friendly, which is a huge bonus for holiday cooking.

What Kind of Potatoes Should I Use?

For the creamiest texture, I always go with Yukon Gold potatoes. They have a natural buttery flavor and smooth consistency that works beautifully when mashed. Russets are another solid option if you prefer an ultra-light, fluffy mash. Whatever you choose, make sure to peel them and boil until fork-tender.

Options for Substitutions

If you’re looking to switch things up, there are several easy substitutions you can make:

Onions: No yellow onions? Sweet onions or even shallots work great.
Cheese: Gruyère is traditional for French onion flavor, but Swiss, provolone, or mozzarella will all melt beautifully.
Butter and Cream: For a dairy-free version, use plant-based butter and oat milk or almond milk.
Potatoes: Cauliflower mash is a lower-carb alternative that also tastes great baked with caramelized onions.

Ingredients for this Twice Baked French Onion Mashed Potatoes

Yukon Gold Potatoes – Their creamy, buttery texture makes them the perfect base for smooth mashed potatoes.
Butter – Adds richness and helps create that luxurious mashed texture.
Heavy Cream – Brings everything together with extra creaminess; can be swapped with whole milk for a lighter version.
Salt and Black Pepper – Essential for seasoning the potatoes and bringing out the natural flavors.
Yellow Onions – The star of the French onion flavor, slowly caramelized to bring out their natural sweetness.
Olive Oil – Used to caramelize the onions to golden perfection.
Gruyère Cheese – Melts beautifully and adds that nutty, savory depth reminiscent of French onion soup.
Garlic (optional) – A clove or two, finely minced, can be added to the caramelized onions for an extra flavor kick.
Fresh Thyme or Parsley (optional garnish) – A fresh herb sprinkle adds color and a touch of brightness before serving.

Step 1: Caramelize the Onions

Start by thinly slicing the onions. In a large skillet over medium-low heat, add olive oil and the onions. Cook slowly, stirring occasionally, for 30–40 minutes until they’re deeply golden and soft. If they start to dry out or burn, add a splash of water to the pan. Optional: Add garlic during the last 5 minutes of cooking.

Step 2: Prepare the Mashed Potatoes

Peel and cut the potatoes into chunks. Boil in salted water for about 15–20 minutes, or until fork-tender. Drain and return to the pot. Add butter, heavy cream, salt, and pepper. Mash until smooth and creamy, adjusting the cream or seasoning as needed.

Step 3: Combine and Layer

Preheat your oven to 375°F (190°C). Fold about two-thirds of the caramelized onions and half the shredded Gruyère into the mashed potatoes. Mix gently to combine.

Step 4: Transfer to Baking Dish

Spoon the mixture into a greased baking dish. Spread it out evenly, then top with the remaining onions and the rest of the cheese.

Step 5: Bake Until Golden

Place the dish in the oven and bake uncovered for 20–25 minutes, or until the top is golden, bubbling, and the cheese is melted to perfection.

Step 6: Garnish and Serve

Remove from the oven and let it rest for 5 minutes. Sprinkle with fresh herbs if desired, and serve warm.

How Long to Prepare the Twice Baked French Onion Mashed Potatoes

Prep Time: Most of the effort goes into caramelizing the onions and mashing the potatoes. The onions take about 30–40 minutes, and the potatoes require about 20 minutes of boiling and 10 minutes of mashing and assembling. So overall, you’re looking at around 50 minutes of active prep time.

Bake Time: Once everything is assembled in the baking dish, the final baking time is 20–25 minutes. This allows the flavors to meld and the top to become golden and cheesy. The total time from start to finish is about 1 hour and 15 minutes, but much of that is hands-off.

Tips for Perfect Twice Baked French Onion Mashed Potatoes

Be patient with the onions. Caramelizing them properly is the key to unlocking the rich, sweet flavor that defines this dish.
Warm the cream and butter before adding to the potatoes. This keeps the mash smooth and fluffy.
Don’t overmix. Once the cheese and onions are added, fold gently to maintain a light texture.
Use a wide skillet for the onions to ensure even caramelization.
Taste as you go. Adjust seasoning in both the onions and the mashed potatoes to your liking before baking.

Watch Out for These Mistakes While Cooking

Rushing the onions: Turning up the heat will brown them too fast and result in bitterness, not sweetness.
Using cold ingredients: Cold cream or butter can lead to gluey mashed potatoes.
Overboiling the potatoes: They’ll absorb too much water and turn watery when mashed.
Underseasoning: Mashed potatoes need salt! Don’t be afraid to add more than you think.
Skipping the final bake: That second bake deepens the flavors and melts everything together beautifully.

What to Serve With Twice Baked French Onion Mashed Potatoes?

1. Herb-Crusted Roast Beef

The savory richness of roast beef pairs beautifully with the sweet onions and creamy potatoes.

2. Garlic Butter Roasted Chicken

A classic choice that complements the flavors without overwhelming them.

3. Seared Pork Chops

The slight sweetness of the onions balances well with savory pork.

4. Steamed Green Beans with Lemon Zest

Adds brightness and freshness to your plate.

5. Mixed Greens Salad with Dijon Vinaigrette

A crisp salad helps lighten up the richness of the dish.

Storage Instructions

Refrigerator: Let leftovers cool completely before transferring to an airtight container. Store in the fridge for up to 4 days. Reheat in the oven at 350°F until warmed through, or microwave individual portions.

Freezer: This dish can be frozen before or after baking. Wrap tightly with foil and freeze for up to 2 months. Thaw overnight in the fridge and reheat in the oven for best texture.

Make-Ahead Tip: You can assemble everything a day ahead and keep it refrigerated until ready to bake. Just add an extra 10 minutes to the bake time if going straight from fridge to oven.

Estimated Nutrition (Per Serving – based on 8 servings)

Calories: 320
Fat: 17g
Saturated Fat: 10g
Carbohydrates: 35g
Fiber: 3g
Sugar: 5g
Protein: 8g
Sodium: 340mg
Cholesterol: 45mg

Frequently Asked Questions

How far in advance can I make this dish?

You can make it 1–2 days in advance and keep it refrigerated until baking.

Can I use red onions instead of yellow?

Yes, but keep in mind they are less sweet and will give the dish a slightly different flavor.

Is this dish gluten-free?

Yes, it’s naturally gluten-free as long as all your ingredients are verified.

What’s the best cheese alternative for Gruyère?

Swiss, provolone, or even a sharp white cheddar are good substitutes that still offer a creamy melt.

Can I skip the second bake?

You could, but you’ll miss out on the beautifully melted cheesy top and the deeper flavor that comes from baking.

Conclusion

Twice Baked French Onion Mashed Potatoes is more than just a side dish—it’s a celebration of everything comforting and flavorful. With rich, creamy potatoes, deeply caramelized onions, and a bubbly baked top, it’s guaranteed to be a hit whether you’re serving it at a holiday feast or as part of a cozy family dinner. Simple ingredients, elevated technique, and a whole lot of heart go into this dish. Give it a try and let it become a new favorite in your kitchen.