ActiveTime50 Mins
Total Time: 2 Hours 5 Mins
Yield: Serves 8 (serving size: 1 1/4 cups)

Classic buttermilk mashed potatoes are great, but if you’re looking to really wow, French Onion Mashed Potatoes are what you need. Perfect for a holiday dinner or other special occasion, these decadent, cheesy mashed potatoes are infused with the rich and comforting flavors of French onion soup. The onions, which are slowly caramelized with thyme and sherry to develop their incredible signature flavor, can be prepared up to 3 days in advance. With finishing touches of nutty Gruyere cheese and a sprinkle of crispy onions for a little textural contrast, our French Onion Mashed Potatoes are ready to steal the spotlight (not to mention, a few hearts) at any table. And for a special twist, try serving the mashed potatoes in individual bubbling ramekins.


  • 1 cup (8 oz.) plus 2 Tbsp. unsalted butter, divided
  • 4 pounds mixed onions (such as yellow onions and red onions), halved and thinly sliced lengthwise (16 cups)
  • 8(6-in.) thyme sprigs, plus leaves for garnish
  • 2 1/2 teaspoons kosher salt, divided
  • 1/3 cup dry sherry
  • 4 pounds Yukon Gold potatoes, peeled and cut into 1/2-in.-thick slices (12 cups)
  • 3 cups half-and-half
  • 1 pound Gruyère cheese, finely shredded (about 4 cups), divided
  • Crispy fried onions (such as French’s), for garnish

How to Make It

Step 1

Melt 4 tablespoons of the butter in a large Dutch oven over medium until sizzling. Stir in onions, thyme, and 2 teaspoons of the salt. Cover and cook, stirring occasionally, until onions are softened and translucent, about 20 minutes. Reduce heat to low; continue to cook, uncovered, stirring occasionally, until onions are jammy and deeply browned, 1 hour 20 minutes to 1 hour 30 minutes. (When they start to stick and burn, add a splash of water, and continue to stir.) Stir in sherry; cook, stirring often, until liquid is absorbed, about 90 seconds. Remove from heat, and stir in 2 tablespoons of the butter until melted. Remove and discard thyme sprigs. 

Step 2

While onions finish cooking, place potatoes in a large pot, and add cold water to cover by 1 inch; lightly salt. Bring to a boil over high. Reduce heat to medium, and simmer, uncovered, until potatoes are fork-tender, 10 to 12 minutes. Drain well in a colander. While still very hot, pass potatoes through ricer into the pot (a potato masher or food mill will also work).

Step 3

Combine half-and-half and remaining 12 tablespoons butter in a medium saucepan over medium-low; cook, stirring occasionally, until butter melts.

Step 4

Return pot of potatoes to low heat. Stir in half-and-half mixture until blended. Gradually stir in 3 1/2 cups of the cheese until melted and smooth. Sprinkle with remaining 1/2 teaspoon salt.

Step 5

Preheat oven to broil with oven rack about 6 inches from heat. Spoon half of the mashed potato mixture into a lightly greased 13- x 9-inch baking dish. Spread 1 1/2 cups of the caramelized onions in an even layer on top. Top with remaining mashed potato mixture. Spread remaining 1/2 cup caramelized onions on top of mashed potatoes. Sprinkle with remaining 1/2 cup cheese. Broil until cheese is melted and browned in spots, 5 to 7 minutes. Garnish with fried onions and thyme leaves.

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