# Components:
→ Potatoes
01 - 3.3 pounds Yukon Gold or russet potatoes, scrubbed and sliced 1/3 inch thick
02 - 2 tablespoons olive oil
03 - 1/2 teaspoon kosher salt
04 - 1/4 teaspoon freshly ground black pepper
→ Caramelized Onions
05 - 3 large yellow onions, thinly sliced
06 - 2 tablespoons unsalted butter
07 - 1 tablespoon olive oil
08 - 1/2 teaspoon kosher salt
09 - 1 teaspoon fresh thyme leaves or 1/2 teaspoon dried thyme
10 - 1 teaspoon balsamic vinegar
→ Topping
11 - 7 ounces Gruyère cheese, grated
12 - 1 ounce Parmesan cheese, grated (optional)
13 - 2 tablespoons chopped fresh parsley, for garnish
# Directions:
01 - Preheat the oven to 425 degrees Fahrenheit and line a large baking sheet with parchment paper.
02 - Toss potato slices with olive oil, kosher salt, and black pepper. Arrange in a single layer on the baking sheet. Roast for 25 to 30 minutes, flipping once halfway through, until golden and tender.
03 - In a large skillet over medium-low heat, melt butter with 1 tablespoon olive oil. Add sliced onions and kosher salt; cook, stirring frequently, for 25 to 30 minutes until deeply golden and caramelized. Stir in thyme leaves and balsamic vinegar; cook for 1 to 2 minutes more, then remove from heat.
04 - Lower oven temperature to 400 degrees Fahrenheit.
05 - Lightly grease a baking dish. Arrange roasted potato slices in a slightly overlapping layer, then evenly spoon caramelized onions over the top. Sprinkle with grated Gruyère and optional Parmesan cheese.
06 - Bake for 10 to 15 minutes until the cheese is melted and bubbling.
07 - Allow to cool slightly. Garnish with chopped fresh parsley before serving warm.