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French Onion Mashed Potato Bake

A square serving of cheesy, baked french onion mashed potato bake with a golden-brown, crispy top.
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Create a comforting, rich side dish by combining creamy mashed potatoes with deeply caramelized onions and melted Gruyère cheese, baked until golden brown.

Ingredients

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  • 3 lbs Russet potatoes, peeled and quartered
  • 1/2 cup whole milk, warmed
  • 4 tablespoons unsalted butter
  • 1 teaspoon salt
  • 1/2 teaspoon black pepper
  • 2 large yellow onions, thinly sliced
  • 2 tablespoons olive oil
  • 1 tablespoon unsalted butter
  • 1/2 cup beef broth
  • 1 teaspoon fresh thyme leaves
  • 1 cup shredded Gruyère cheese, divided
  • 1/2 cup shredded Swiss cheese

Instructions

  1. Place the peeled and quartered potatoes in a large pot and cover with cold, salted water. Bring to a boil and cook until fork-tender, about 15 to 20 minutes.
  2. While potatoes cook, prepare the onions. Heat olive oil and 1 tablespoon of butter in a large skillet over medium-low heat. Add the sliced onions and cook slowly, stirring occasionally, for 25 to 35 minutes until they are deep golden brown and soft. This slow cooking develops the flavor.
  3. Once onions are caramelized, stir in the beef broth and thyme. Cook until the liquid evaporates, about 2 minutes. Remove from heat and set aside.
  4. Drain the cooked potatoes well. Return them to the hot pot over low heat for one minute to dry out any remaining moisture.
  5. Remove the pot from the heat. Add the warm milk and 4 tablespoons of butter to the potatoes. Mash until smooth. Stir in the salt and pepper.
  6. Gently fold half of the caramelized onions into the mashed potatoes.
  7. Preheat your oven to 375 degrees Fahrenheit. Lightly grease an 8×8 inch baking dish.
  8. Spread the mashed potato mixture evenly into the prepared baking dish. Top with the remaining caramelized onions.
  9. In a small bowl, mix the Gruyère and Swiss cheeses. Sprinkle two-thirds of the cheese mixture evenly over the top of the potatoes.
  10. Bake for 20 minutes. Remove from the oven, sprinkle with the remaining cheese, and bake for another 5 to 10 minutes, or until the cheese is melted and bubbly and the edges are lightly browned.
  11. Let the potato bake rest for 5 minutes before serving.

Notes

  • For the best flavor, do not rush caramelizing the onions; low and slow heat prevents burning and maximizes sweetness.
  • You can prepare the mashed potatoes and onions a day ahead. Store them separately in the refrigerator and assemble before baking.
  • If you do not have beef broth, use vegetable broth or water mixed with a small amount of Worcestershire sauce for depth.

Nutrition

Find it online: https://tastethisplate.com/french-onion-mashed-potato-bake/