French Onion Potato Gratin
French Onion Potato Gratin
Ingredients
For the Caramelized Onions and Cream Sauce
- 2 tablespoons olive oil
- 2 yellow onions, large, thinly sliced
- 1 teaspoon sugar
- 1 teaspoon salt
- 3 cloves garlic, minced
- 1 teaspoon thyme, chopped
- 2 teaspoons Worcestershire sauce
- 2 tablespoons unsalted butter
- 1 1/2 tablespoons all-purpose flour
- 1 cup heavy cream
- 1/4 cup Hellmann’s mayonnaise
- 1/2 teaspoon black pepper
For the Gratin Assembly
- 3 pounds Yukon Gold potatoes, peeled and thinly sliced (about 1/8-inch)
- 1 cup Gruyère cheese, shredded
- 1/4 cup Parmesan cheese, grated
- as needed unsalted butter, for greasing
Instructions
- 1
Preheat the oven to 375°F. Grease a 9x13-inch baking dish generously with butter.
⏱️ 5 min•🌡️ 375
- 2
In a large skillet, add the olive oil over medium heat. Add the thinly sliced yellow onions, sugar, and 1 teaspoon of salt. Cook slowly, stirring occasionally, until the onions are deep golden brown and caramelized, about 25–30 minutes.
⏱️ 30 min
- 3
Stir in the minced garlic and chopped thyme and cook for 1 more minute. Deglaze the pan with Worcestershire sauce, scraping off any brown bits from the bottom of the pan.
⏱️ 2 min
- 4
Add the unsalted butter to the pan, stirring frequently until melted.
⏱️ 1 min
- 5
Add in the all-purpose flour and continue cooking, stirring frequently until the flour is lightly golden, 2-3 minutes.
⏱️ 3 min
- 6
Pour in the heavy cream, 3/4 cup of the shredded Gruyère cheese (reserve 1/4 cup for the top), and the Hellmann’s mayonnaise. Whisk until the cheese is melted and the mixture is creamy. Season with 1/2 teaspoon of black pepper and salt to taste.
⏱️ 5 min
- 7
In a large bowl, pour the cream mixture over the thinly sliced potatoes and toss until the potatoes are well coated.
⏱️ 5 min
- 8
Take a stack of the coated potatoes and line the greased baking dish, keeping the potatoes upright. Repeat this process until all potatoes have been used. Scrape any leftover cream mixture over the potatoes.
⏱️ 10 min
- 9
Sprinkle the remaining 1/4 cup of reserved Gruyère cheese and the grated Parmesan cheese over the top of the potatoes.
⏱️ 1 min
- 10
Cover the baking dish with foil and bake for 40 minutes.
⏱️ 40 min•🌡️ 375
- 11
Remove the foil and bake for an additional 20–25 minutes, until the top is golden brown and the potatoes are tender when pierced with a knife.
⏱️ 25 min•🌡️ 375
- 12
Let the gratin rest for 10 minutes before serving.
⏱️ 10 min
Kitchen Tools
Nutrition Facts (per serving)
French Onion Potato Gratin
For the Caramelized Onions and Cream Sauce
- 2 tablespoons olive oil
- 2 yellow onions, large, thinly sliced
- 1 teaspoon sugar
- 1 teaspoon salt
- 3 cloves garlic, minced
- 1 teaspoon thyme, chopped
- 2 teaspoons Worcestershire sauce
- 2 tablespoons unsalted butter
- 1 1/2 tablespoons all-purpose flour
- 1 cup heavy cream
- 1/4 cup Hellmann’s mayonnaise
- 1/2 teaspoon black pepper
For the Gratin Assembly
- 3 pounds Yukon Gold potatoes, peeled and thinly sliced (about 1/8-inch)
- 1 cup Gruyère cheese, shredded
- 1/4 cup Parmesan cheese, grated
- as needed unsalted butter, for greasing
Instructions
- 1
Preheat the oven to 375°F. Grease a 9x13-inch baking dish generously with butter.
⏱️ 5 min•🌡️ 375 - 2
In a large skillet, add the olive oil over medium heat. Add the thinly sliced yellow onions, sugar, and 1 teaspoon of salt. Cook slowly, stirring occasionally, until the onions are deep golden brown and caramelized, about 25–30 minutes.
⏱️ 30 min - 3
Stir in the minced garlic and chopped thyme and cook for 1 more minute. Deglaze the pan with Worcestershire sauce, scraping off any brown bits from the bottom of the pan.
⏱️ 2 min - 4
Add the unsalted butter to the pan, stirring frequently until melted.
⏱️ 1 min - 5
Add in the all-purpose flour and continue cooking, stirring frequently until the flour is lightly golden, 2-3 minutes.
⏱️ 3 min - 6
Pour in the heavy cream, 3/4 cup of the shredded Gruyère cheese (reserve 1/4 cup for the top), and the Hellmann’s mayonnaise. Whisk until the cheese is melted and the mixture is creamy. Season with 1/2 teaspoon of black pepper and salt to taste.
⏱️ 5 min - 7
In a large bowl, pour the cream mixture over the thinly sliced potatoes and toss until the potatoes are well coated.
⏱️ 5 min - 8
Take a stack of the coated potatoes and line the greased baking dish, keeping the potatoes upright. Repeat this process until all potatoes have been used. Scrape any leftover cream mixture over the potatoes.
⏱️ 10 min - 9
Sprinkle the remaining 1/4 cup of reserved Gruyère cheese and the grated Parmesan cheese over the top of the potatoes.
⏱️ 1 min - 10
Cover the baking dish with foil and bake for 40 minutes.
⏱️ 40 min•🌡️ 375 - 11
Remove the foil and bake for an additional 20–25 minutes, until the top is golden brown and the potatoes are tender when pierced with a knife.
⏱️ 25 min•🌡️ 375 - 12
Let the gratin rest for 10 minutes before serving.
⏱️ 10 min