French Onion Mashed Potatoes

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These French onion mashed potatoes take everyone’s favorite side dish to a completely new level. Rich caramelized onions are infused in buttery potatoes with gooey gruyere cheese and herbs. The potatoes are boiled in a beef broth mixture for added flavor that makes these potatoes even closer to French onion soup flavor.

Dish with french onion topped mashed potatoes with serving spoon.

Why We Love These French Onion Mashed Potatoes

French onion soup lovers, we took the flavors and what makes the soup so rich and flavorful and combined it with rich, creamy mashed potatoes. This will be a favorite side dish for the holiday spread, a special dinner and more.

Potatoes simmered in beef broth, and them mashed and combined with caramelized onions, gruyere cheese, fresh thyme and more–these will be a huge hit!

These French onion mashed potatoes:

take extra time to prep, but the actual preparation is simple and straightforward
are so rich and flavorful, and like no other potato dish you have had
will be the star of the show on the Thanksgiving menu
easily pair with a variety of main dishes beyond just the holiday roast turkey including Maple Bacon Wrapped Pork Chops, Slow Cooker Beef Tips, Grilled Balsamic Chicken and much more.

Serve these potatoes with Apple Sage Stuffing, Cheesy Cornbread Casserole, Maple Dijon Brussels Sprouts and Sweet Potatoes, these No Yeast Dinner Rolls and more!

Ingredient Notes

Potatoes, onions, butter, herbs and other ingredients labeled on surface.

Yukon gold potatoes are our preference for mashed potatoes, but using a combo of yukon and russet potatoes is also a great option. Yukon golds make for a rich, creamy mashed potato and russets make more light and fluffy potatoes so if you have a bit of each, it creates a balance of the two.
Dry sherry is often used in French onion soup, but I opted for a splash of balsamic vinegar instead in the onions to keep the ingredients closer to kitchen staples. Feel free to use dry sherry or a splash of white wine instead.
If you can’t find gruyere cheese, you can use Swiss cheese or I often see a cheddar gruyere combo at the store that is good.
Sweet yellow onions are ideal for caramelizing as they have a balanced flavor. I don’t recommend red onions as they have less sweetness overall.

Ways To Vary This Recipe

add breadcrumbs: classic French onion soup comes with bread as well but I found that to be a bit too much, but feel free to add some buttery toasted breadcrumbs over top to round it out.
add an extra layer of flavor: stir in Worcestershire sauce, other fresh herbs, some fresh parmesan cheese, and more
lighten it up a bit: instead of heavy cream, use a bit of half and half or even some whole milk or use Greek yogurt instead of sour cream to make this dish a bit less rich

Step-By-Step Instructions

Step 1: Prepare the onions: Heat the butter and oil in a large skillet over medium heat. Add the onions and sauté for 7-10 minutes, until they begin to soften.

Caramelized onions with balsamic added in pan.

Step 2: Reduce to medium-low heat and cook for about 50 minutes to 1 hour, stirring every several minutes, or until the onions are golden brown, and caramelized. Timing can vary. When onions are caramelized, add sea salt and a splash of balsamic vinegar or dry sherry if desired and stir to combine.

Step 3: When the onions are about 25 minutes into cooking, add cut, 2-inch pieces of potatoes along with the garlic and salt to a large pot with cold water that covers the potatoes by about an inch. Add beef broth as well if desired. Once boiling, reduce to medium heat and gently boil for about 15 minutes or until the potatoes are fork tender (you can easily poke a fork through the potato).

Mashed potatoes with added butter, sour cream, gruyere cheese and herbs.

Step 4: Drain the potatoes well. Return potatoes to the pot, allowing the potatoes to sit on the hot burner for a minute or so to dry out more. Once the potatoes are drained and dried out of excess water, use a potato masher to start mashing the potatoes. Add the melted butter, cream, shredded cheese, pepper, thyme and sour cream and continue mashing until blended, cheese is melted and the potatoes are desired consistency. You can add more cream or milk if they seem too thick.

Caramelized onions added to pot with mashed potatoes.

Step 5: Gently fold in about two-thirds of the caramelized onions.

Prepared French onion mashed potatoes in pot with wooden spoon.

Step 6: Adjust texture and seasoning before serving with remaining onions over top.

Recipe Tips

Gently boiling the potatoes keeps them from becoming too water logged. Once the water is begins to boil, shift the heat to medium and keep the potatoes at a gentle boil versus a vigorous boil.

Use room temperature or even slightly warmed dairy when adding to the potatoes. This allows for quicker absorption and you won’t need to stir the potatoes as much which can lead to gummier potatoes if over-stirred.

Make sure the potatoes are drained well before mashing. Drain the water and then let the potatoes sit for a few minutes in the hot pot to allow any extra water to dry out.

Serving dish with French onion mashed potatoes topped with balsamic caramelized onions.

Common Questions

Can I make these potatoes ahead of time?

Yes! You can make these a day in advance. Prepare recipe as written and store in the refrigerator in an airtight container. Our preferred reheating method is in the slow cooker on low for about 1 1/2 -2 hours. Add an extra splash of milk or cream if they seem a bit dry. When making in advance, try to stir the potatoes as little as possible when initially preparing.

I don’t suggest reheating in the microwave for anything more than a serving or two, but it can work in a pinch.