French Onion Potato Gratin (Printable)

Tender roasted potatoes topped with richly caramelized onions and melted Gruyère cheese.

# Required Ingredients:

→ Potatoes

01 - 4 large Yukon Gold potatoes, scrubbed and sliced into 1/2-inch rounds
02 - 2 tablespoons olive oil
03 - 1/2 teaspoon kosher salt
04 - 1/4 teaspoon black pepper

→ Caramelized Onions

05 - 2 large yellow onions, thinly sliced
06 - 2 tablespoons unsalted butter
07 - 1 tablespoon olive oil
08 - 1/2 teaspoon sugar
09 - 1/4 teaspoon salt
10 - 1 teaspoon fresh thyme leaves or 1/2 teaspoon dried thyme

→ Topping

11 - 1 cup (100 grams) Gruyère cheese, grated
12 - 2 tablespoons fresh parsley, chopped (optional garnish)

# Preparation Steps:

01 - Preheat the oven to 425°F. Line a baking sheet with parchment paper.
02 - Toss potato slices with olive oil, kosher salt, and black pepper in a large bowl. Arrange them in a single layer on the prepared baking sheet. Roast for 25 to 30 minutes, flipping halfway through, until golden and tender.
03 - While potatoes roast, heat butter and olive oil in a large skillet over medium-low heat. Add sliced onions and salt, cooking and stirring frequently until softened, about 10 minutes. Sprinkle in sugar and thyme, then continue to cook, stirring occasionally, until onions turn deeply golden and caramelized, about 20 to 25 minutes. Reduce heat if onions brown too quickly.
04 - Remove potatoes from the oven and arrange them in a shallow ovenproof baking dish or skillet, slightly overlapping the slices.
05 - Evenly spread the caramelized onions over the potatoes. Sprinkle grated Gruyère cheese on top.
06 - Return the dish to the oven and bake for 10 to 12 minutes until the cheese melts and bubbles. For additional browning, broil for 2 to 3 minutes if desired.
07 - Garnish with chopped fresh parsley and serve immediately while hot.

# Expert Suggestions:

01 -
  • It tastes like French onion soup but arrives on your plate as a golden, crispy-edged potato cake—no spoon required.
  • The caramelized onions do most of the work while your potatoes roast, so you're not actually hovering over the stove the whole time.
  • Gruyère melts into every crevice, and people genuinely ask for the recipe before they've even finished eating.
02 -
  • Caramelized onions take patience—rush them and you get brown onions, not caramelized ones, and that's a completely different taste.
  • Don't skip flipping the potatoes halfway through roasting; the side that hits the pan first browns beautifully, and the other side needs equal time.
  • If your cheese isn't melting evenly, your potatoes aren't hot enough from the first roast; give them those full 25–30 minutes.
03 -
  • Use a mandoline slicer for your potatoes if you have one—uniform thickness means they cook at the same rate, and you won't end up with some pieces creamy and others crunchy in the wrong way.
  • Don't wash your potato slices after cutting them, even though it removes starch; the starch actually helps them brown and stick together slightly, creating better texture.
Go Back