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Caramelized Onion and Potato Gratin topped with gruyere cheese.
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5 from 2 votes

Caramelized Onion and Potato Gratin

A creamy, cheesy potato gratin flavored with caramelized onions and fresh thyme.
Course Side Dish
Servings 8


  • 2 tablespoons unsalted butter
  • 3 cups chopped onions, about 2 large or 3 medium
  • 2 teaspoons salt
  • 1 tablespoon brown sugar
  • 1 cup low-sodium chicken broth
  • 2/3 cup white wine
  • 2/3 cup heavy cream
  • 1 teaspoon balsamic vinegar
  • 3 pounds russet potatoes, I used a combo of russets and sweet potatoes, peeled and sliced 1/8-inch thick
  • 2 teaspoons minced fresh thyme
  • 1 teaspoon pepper
  • 1 1/2 cups shredded Gruyere cheese


  • Position an oven rack in the middle of oven and heat oven to 350 degrees.
  • Melt butter in a large nonstick skillet over medium-high heat. Add onions and 1 teaspoon salt. Cook until onions are just starting to brown, about 5 minutes.
  • Stir in brown sugar and continue to cook for about 5 minutes, stirring frequently. Onions should be golden brown.
  • Add 1/3 cup broth and cook 5 additional minutes. Mixture should be golden brown and sticky. Transfer onions to medium bowl.
  • Add remaining broth plus wine, cream, and remaining 1 teaspoon salt to skillet and bring to a boil. Scrape any browned bits off bottom. Once at a boil, remove from heat and stir in vinegar. Cover and keep warm.
  • In a 3-quart casserole dish, arrange half of potatoes so that they are overlapping. Sprinkle with 1 teaspoon thyme and 1/2 teaspoon pepper.
  • Spread all of caramelized onions on top.
  • Top with remaining potatoes, thyme, and pepper. Pour broth mixture over the top.
  • Place in oven and bake 30 minutes. Remove from oven and top with cheese. Place back in oven for 30 to 40 minutes. Let cool 15 minutes before serving.