French Onion Potato Gratin (Printable)

Slices of golden potatoes topped with caramelized onions and bubbling Gruyère cheese for a comforting dish.

# What You'll Need:

→ Potatoes

01 - 4 large Yukon Gold potatoes, scrubbed and sliced into ½-inch rounds
02 - 2 tablespoons olive oil
03 - ½ teaspoon kosher salt
04 - ¼ teaspoon black pepper

→ Caramelized Onions

05 - 2 large yellow onions, thinly sliced
06 - 2 tablespoons unsalted butter
07 - 1 tablespoon olive oil
08 - ½ teaspoon sugar
09 - ¼ teaspoon salt
10 - 1 teaspoon fresh thyme leaves (or ½ teaspoon dried)

→ Topping

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

# How to Make It:

01 - Preheat oven to 425°F. Line a baking sheet with parchment paper. Toss potato slices with olive oil, kosher salt, and black pepper in a large bowl. Arrange in a single layer on the prepared sheet.
02 - Roast potatoes for 25 to 30 minutes, flipping them 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 often until softened, about 10 minutes. Sprinkle in sugar and thyme, then continue cooking, stirring occasionally, until onions turn deeply golden and caramelized, about 20 to 25 minutes. Reduce heat if they brown too quickly.
04 - Remove potatoes from oven and arrange in a shallow ovenproof dish or skillet, slightly overlapping slices. Spread caramelized onions evenly over potatoes.
05 - Sprinkle grated Gruyère cheese evenly on top of the onions.
06 - Return dish to oven and bake for 10 to 12 minutes until cheese is melted and bubbling. Optionally broil for 2 to 3 minutes to brown the cheese further.
07 - Garnish with chopped parsley and serve hot.

# Expert Tips:

01 -
  • It tastes like French onion soup but you can eat it with a fork, no messy bread bowls required.
  • The caramelization process is oddly meditative, and your whole kitchen smells incredible for hours.
  • Golden potatoes and melted cheese together feel fancy but take minimal hands-on time once the onions are going.
02 -
  • Patience with onions is non-negotiable; rushing them over high heat gives you brown onions, not caramelized ones, and there's a real difference in flavor and texture.
  • Slicing onions uniformly matters more than you'd think because thin slices caramelize evenly, while thick pieces stay chewy in the middle.
  • The oven temperature matters for potatoes—425°F is hot enough to crisp the edges while cooking the insides, but 400°F works if that's more comfortable for your oven.
03 -
  • Save the potato scrubbing water—if it's starchy, use it to give your potatoes extra crispiness by tossing them in the starch before the oil.
  • If your oven runs hot, lower the temperature by 25 degrees and check the potatoes a few minutes early rather than risk burnt edges and raw centers.
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