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Side view of French onion mashed potatoes in a white serving bowl with onions and potatoes in the background
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French Onion Mashed Potatoes

Recipe for French Onion Mashed Potatoes, these homemade creamy mashed potatoes are mixed with sweet caramelized onions and Gruyère cheese for that ultimate comfort food flavor.
Course Side Dish
Cuisine French inspired, Fusion, International
Keyword Caramelized onions, Comfort food, Gruyère cheese, Mashed potatoes
Prep Time 25 minutes
Cook Time 1 hour 15 minutes
Total Time 1 hour 40 minutes
Servings 10

Ingredients

  • ½ cup unsalted butter, divided 113 grams (1 stick)
  • 2 medium yellow onions finely sliced
  • 4 pounds Yukon gold potatoes about 8-10 potatoes, 1.8 kg
  • 2 teaspoons salt divided
  • 1 cup heavy whipping cream 240 ml
  • ½ teaspoon ground thyme
  • 1 teaspoon garlic powder
  • 1 cup shredded Gruyère 115 grams
  • 1 teaspoon black pepper
  • Fresh parsley for garnish optional

Instructions

  • In a large skillet, melt 3 tablespoons of butter over medium heat. Add the sliced onions and stir so that the onions are lightly coated in the butter.
    Sliced white onions in a skillet
  • Let cook for 25 minutes, stirring often.
    Sliced white onions cooking in a skillet
  • Then reduce the heat to medium-low and continue cooking until the onions are fully browned and jammy, about 45-55 more minutes. Once fully caramelized, remove them from the heat and set aside.
    Overhead view of a skillet with caramelized onions
  • Meanwhile, wash and peel the potatoes and cut them into 1-inch cubes. Add them to a large pot and fill the pot with water until the potatoes are covered. Stir in 1 teaspoon salt and place the pot over medium-high heat.
    Diced potatoes cooking in a pot of water
  • Bring to a boil, and then reduce the heat to medium, cover, and let simmer for 10-15 minutes or until the potatoes are fork tender. Remove from the heat and drain.
    Cooked and drained potato chunks in a copper pot
  • Use a potato masher to mash the potatoes until mostly smooth. Set aside.
    Potatoes being mashed with a potato masher
  • Melt 2 tablespoons of butter in a small saucepan over medium heat. Once melted, add the heavy whipping cream, ground thyme, and garlic powder. Bring to a simmer, stirring often. Remove from the heat and pour into the pot with the potatoes. Use the potato masher to combine the cream mixture with the potatoes.
    Melted butter being added to a pot of mashed potatoes
  • Once smooth, add in the Gruyère, the remaining 1 teaspoon salt, the black pepper, the remaining 3 tablespoons butter, and all but ½ cup of the caramelized onions.
    Caramelized onions, gruyère cheese and butter being added to a pot of mashed potatoes
  • Stir the mashed potatoes until fully combined.
    Overhead view of mashed potatoes in a large pot
  • Top the potatoes with the remaining caramelized onions and garnish with chopped parsley. Serve warm.
    Overhead view of a serving bowl with mashed potatoes topped with caramelized onions

Notes

  • You want your potato pieces to be roughly the same size so that they cook evenly.
  • Mash the potatoes just until they are smooth. Overmashing can make the potatoes gluey instead of light and fluffy.