I love this recipe because it transforms simple ingredients into something that tastes restaurant-worthy. The slow-cooked onions bring deep sweetness, the potatoes get crispy and golden, and the Gruyère melts into a bubbling top layer that pulls everything together. It’s hearty, elegant, and totally satisfying.
Ingredients
(Here’s a tip: Check out the full list of ingredients and measurements in the recipe card below.)
I heat 2 tablespoons of olive oil in a large cast-iron skillet over medium heat. I add the onions and 1 teaspoon salt, reduce the heat to medium-low, and cook—stirring occasionally—until deeply golden, about 30–40 minutes.
I add the sherry and cook for 1 minute, scraping up any browned bits. I transfer the onions to a bowl and set them aside. I rinse and wipe the skillet clean.
Par-cook the potatoes
While the onions cook, I place the sliced potatoes in a saucepan, cover with water by 1 inch, and add 1 tablespoon salt. I bring it to a boil and cook for about 3 minutes, until just fork-tender. I drain and place the potatoes in a single layer on a paper towel-lined baking sheet to dry.
Crisp the potatoes
I line another baking sheet with paper towels. In the clean skillet, I heat 2 tablespoons butter and 1/2 tablespoon oil over medium-high heat. I add half the potatoes in a single layer and season with 3/4 teaspoon salt. I cook undisturbed for 3–5 minutes per side, until golden brown.
I transfer them to the towel-lined baking sheet and repeat the process with the remaining butter, oil, potatoes, and salt.
Assemble and broil
I return all the browned potatoes to the skillet, stir in the caramelized onions, remaining 1/2 teaspoon salt, and black pepper.
I preheat the oven to broil, with a rack 6 inches from the heat source. I sprinkle the top with shredded Gruyère and broil for 3–5 minutes until melted and bubbly.
I use red onions for a slightly different flavor and color.
I add a splash of balsamic vinegar instead of sherry for a sweet-tangy finish.
I layer in some sautéed mushrooms for extra depth.
I sprinkle crushed garlic into the onions during the last 5 minutes of caramelizing for a bolder taste.
I swap Gruyère for fontina or sharp white cheddar if I want a different cheese profile.
storage/reheating
I store leftovers in an airtight container in the refrigerator for up to 3 days. To reheat, I place them in a 350°F oven until hot and bubbly, about 15–20 minutes. I avoid microwaving if I want to keep the potatoes crispy.
FAQs
Can I make this ahead of time?
Yes, I often caramelize the onions up to three days ahead or freeze them for longer storage. I assemble and broil just before serving.
Can I use a different cheese?
Yes, I sometimes use fontina, gruyère-style Swiss, or even sharp white cheddar if I want a more accessible option.
Do I have to peel the potatoes?
No, I can leave the skins on if I prefer a more rustic texture.
Can I use a different kind of potato?
Yukon gold works best for their creamy texture, but I’ve also used red or russet potatoes in a pinch.
Is the sherry necessary?
I love the depth it adds, but I can substitute with a splash of white wine or skip it if needed.
Conclusion
I love how French onion Lyonnaise potatoes blend the savory comfort of caramelized onions with crisp, buttery potatoes and melty cheese. This dish is hearty, elegant, and full of flavor—ideal for special dinners or whenever I want something a little extra. It’s one of those recipes that always brings compliments to the table.
1 1/2 pounds Yukon gold potatoes (about 4 medium), peeled and sliced into 1/4-inch rounds
4 tablespoons unsalted butter, divided
1/2 teaspoon black pepper
4 ounces Gruyère cheese, shredded (about 1 cup)
1 teaspoon fresh thyme leaves
Instructions
Caramelize Onions:
Heat 2 tablespoons olive oil in a large cast-iron skillet over medium heat. Add onions and 1 teaspoon salt. Reduce heat to medium-low and cook, stirring occasionally, until onions are deep golden brown, 30–40 minutes. Add sherry and cook, stirring and scraping the bottom of the skillet, until absorbed, about 1 minute. Transfer to a bowl and set aside. Wipe skillet clean.
Parcook Potatoes:
While onions cook, place sliced potatoes in a medium saucepan with 1 tablespoon salt and enough water to cover by 1 inch. Bring to a boil over high heat and cook until just tender, about 3 minutes. Drain well and place on a paper towel–lined baking sheet. Pat dry and set aside.
Brown Potatoes:
Line a baking sheet with paper towels. Heat 2 tablespoons butter and 1/2 tablespoon oil in the clean skillet over medium-high. Add half of the potatoes in a single layer. Sprinkle with 3/4 teaspoon salt. Cook undisturbed until golden brown on one side, 3–5 minutes. Flip and brown the other side, another 3–5 minutes. Transfer to lined baking sheet. Repeat with remaining butter, oil, potatoes, and salt.
Combine Ingredients:
Return all browned potatoes to skillet. Add caramelized onions, black pepper, and remaining 1/2 teaspoon salt. Stir gently to combine.
Broil and Finish:
Preheat oven broiler with rack 6 inches from heat source. Sprinkle Gruyère evenly over potatoes. Broil for 3–5 minutes, until cheese melts and bubbles. Remove from oven, sprinkle with fresh thyme, and serve hot.
Notes
Caramelized onions can be made up to 3 days ahead or frozen for up to 1 month.
Assemble and broil the day of serving for best results.
Use a mandoline for evenly sliced potatoes to ensure even cooking.
