French Onion Potatoes au Gratin
Ingredients
- 4 tbsp. salted butter
plus more for the baking dish
- 2 tbsp. olive oil
- 5 onions
thinly sliced
- 1 1/2 tsp. kosher salt
- to tasteBlack pepper
- 1 tsp. sugar
- 1 tbsp. fresh thyme
chopped
- 1/4 c. dry sherry
- 1/2 c. low-sodium beef broth
- 2 tbsp. all-purpose flour
- 1 1/2 c. heavy cream
- 1 1/2 c. whole milk
- 1/4 tsp. freshly grated nutmeg
- 6 oz. gruyere cheese
shredded
- 6 oz. swiss cheese
shredded
- 5 large russet potatoes
peeled, halved and sliced 1/4 inch thick
- 1/4 c. grated parmesan cheese
- Chopped fresh chives
for topping
Directions
- 1
Preheat the oven to 375˚. Butter a 9-by-13-inch baking dish. Heat the olive oil and 2 tablespoons butter in a large skillet over medium-low heat. Add the onions, 1 teaspoon salt, a few grinds of pepper and the sugar. Stir, then cover and cook, stirring once, 10 minutes. Uncover, increase the heat to medium and cook, stirring, 10 more minutes. Add the thyme, sherry and broth. Cook, stirring, until the liquid evaporates and the onions are caramelized, about 15 more minutes.
- 2
Melt the remaining 2 tablespoons butter in a dutch oven over medium heat. Stir in the flour and cook 1 minute, then whisk in the heavy cream and milk. Add the remaining ½ teaspoon salt and the nutmeg. Bring to a simmer, whisking until smooth. Cook, stirring, until thickened, 2 to 3 minutes. Remove from the heat. Stir in all but ½ cup each of the gruyère and Swiss until melted. Stir in the potatoes.
- 3
Layer half of the potatoes in the baking dish, then half of the onions. Repeat with the remaining potatoes and onions. Sprinkle with the reserved gruyère and Swiss and the parmesan. Cover with foil, tenting it so it doesn’t touch the cheese; bake until the potatoes are tender, 45 to 55 minutes. Uncover and bake until golden brown, 20 to 25 minutes. Let sit 20 minutes before serving. Top with chives.
French Onion Potatoes au Gratin
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Ratings & Reviews
Based on 2 ratings
Rating Breakdown
About this Recipe
Imagine the rich, savory depth of classic French onion soup transformed into the ultimate comforting side dish. This French Onion Potatoes au Gratin recipe brings together tender, thinly sliced potatoes with sweet caramelized onions and a creamy, cheesy sauce for an unforgettable experience.
What sets this gratin apart is the meticulous layering of flavors. We marry the slow-cooked, deeply savory sweetness of caramelized onions with a silky, nutmeg-infused cream sauce, ensuring every forkful is a perfect balance of earthy potato and umami richness, all crowned with a golden, bubbly cheese crust.
Prepare yourself for a truly luxurious side that's both hearty and refined. You'll savor the tender bite of perfectly cooked russet potatoes enveloped in a rich, creamy sauce that's subtly sweet from the caramelized onions and aromatic with fresh thyme. The combination of Gruyère and Swiss cheeses melts into an irresistible, gooey blanket, with a hint of sharp Parmesan on top, offering a comforting warmth perfect for any gathering. It’s an indulgence that promises to be the star of your dinner table, not just a supporting player.
Customization & Variations
While this recipe shines as is, you can easily adapt it to your pantry or preferences.
- For a milder cheese profile, consider swapping out some Gruyère for white cheddar.
- If you don't have dry sherry, a dry white wine can offer a similar acidic lift to the caramelized onions.
- For a deeper herbal note, fresh rosemary could complement the thyme beautifully.
This impressive French Onion Potatoes au Gratin is ideal for holiday feasts, special Sunday dinners, or any occasion where you want to serve a truly memorable side dish. It pairs beautifully with roasted meats like beef tenderloin or a classic roasted chicken.