French Onion Green Bean Casserole
French Onion Green Bean Casserole
Ingredients
For the Caramelized Onions
- 2 white onions, large, thinly sliced
- 2 tablespoons unsalted butter
- 1 tablespoon olive oil
- 1/2 teaspoon kosher salt, plus more as needed
- 1/4 teaspoon black pepper, freshly ground, plus more as needed
For the Green Beans
- 1 pound fresh green beans, trimmed
- 1 teaspoon kosher salt, for blanching water
- as needed water, for blanching
- as needed ice, for ice bath
For the Mushroom Cream Sauce
- 3 tablespoons unsalted butter
- 8 ounces cremini mushrooms, sliced
- 3 tablespoons all-purpose flour
- 1 1/2 cups whole milk
- 1/2 cup chicken broth, low sodium
- 1/2 teaspoon kosher salt, plus more as needed
- 1/4 teaspoon black pepper, freshly ground, plus more as needed
- 1/4 teaspoon nutmeg, freshly grated
For the Topping
- 4 ounces Gruyère cheese, freshly grated (about 1 cup)
- 1 1/2 cups croutons, store-bought or homemade
- 2 tablespoons unsalted butter, melted (if using plain croutons)
Instructions
- 1
Caramelize the Onions: In a large skillet, melt 2 tablespoons of unsalted butter and 1 tablespoon of olive oil over medium-low heat. Add the thinly sliced white onions and season with 1/2 teaspoon of kosher salt and 1/4 teaspoon of black pepper. Cook slowly, stirring occasionally, until the onions are deeply golden brown, sweet, and tender, about 30-40 minutes. Set aside.
⏱️ 40 min
- 2
Prepare the Green Beans: Bring a large pot of water to a rolling boil. Add 1 teaspoon of kosher salt to the water. Prepare a large bowl with ice and water for an ice bath. Add the trimmed fresh green beans to the boiling water and blanch for 3-4 minutes, until they are crisp-tender and vibrant green. Immediately transfer the blanched green beans to the ice bath to stop the cooking process. Once cooled, drain them thoroughly.
⏱️ 10 min
- 3
Make the Mushroom Cream Sauce: In a medium saucepan, melt 3 tablespoons of unsalted butter over medium heat. Add the sliced cremini mushrooms and sauté until they are softened and lightly browned, about 5-7 minutes. Sprinkle in 3 tablespoons of all-purpose flour and cook, stirring constantly, for 1-2 minutes to create a roux. Gradually whisk in 1 1/2 cups of whole milk and 1/2 cup of chicken broth until the sauce is smooth and begins to thicken. Bring to a gentle simmer, stirring frequently, then reduce the heat to low and cook for 5 minutes, or until the sauce coats the back of a spoon. Season with 1/2 teaspoon of kosher salt, 1/4 teaspoon of black pepper, and 1/4 teaspoon of freshly grated nutmeg. Taste and adjust seasoning as needed.
⏱️ 15 min
- 4
Preheat Oven and Prepare Dish: Preheat your oven to 375°F. Lightly grease a 9x13 inch baking dish.
⏱️ 5 min•🌡️ 375
- 5
Assemble the Casserole: Spread the drained blanched green beans evenly in the prepared baking dish. Pour the homemade mushroom cream sauce over the green beans, ensuring they are well coated. Distribute the caramelized onions in an even layer over the sauce. Sprinkle the freshly grated Gruyère cheese evenly over the caramelized onions. If your croutons are plain, toss them with 2 tablespoons of melted unsalted butter, then scatter them over the cheese layer.
⏱️ 10 min
- 6
Bake the Casserole: Bake the casserole in the preheated oven for 25-30 minutes, or until it is bubbly around the edges, the cheese is melted and slightly golden brown, and the croutons are crispy. If the croutons are browning too quickly, you can loosely tent the casserole with aluminum foil.
⏱️ 30 min•🌡️ 375
- 7
Serve: Remove the casserole from the oven and let it stand for a few minutes before serving to allow the sauce to set slightly. Serve hot.
Kitchen Tools
Nutrition Facts (per serving)
French Onion Green Bean Casserole
Ingredients
For the Caramelized Onions
- 2 white onions, large, thinly sliced
- 2 tablespoons unsalted butter
- 1 tablespoon olive oil
- 1/2 teaspoon kosher salt, plus more as needed
- 1/4 teaspoon black pepper, freshly ground, plus more as needed
For the Green Beans
- 1 pound fresh green beans, trimmed
- 1 teaspoon kosher salt, for blanching water
- as needed water, for blanching
- as needed ice, for ice bath
For the Mushroom Cream Sauce
- 3 tablespoons unsalted butter
- 8 ounces cremini mushrooms, sliced
- 3 tablespoons all-purpose flour
- 1 1/2 cups whole milk
- 1/2 cup chicken broth, low sodium
- 1/2 teaspoon kosher salt, plus more as needed
- 1/4 teaspoon black pepper, freshly ground, plus more as needed
- 1/4 teaspoon nutmeg, freshly grated
For the Topping
- 4 ounces Gruyère cheese, freshly grated (about 1 cup)
- 1 1/2 cups croutons, store-bought or homemade
- 2 tablespoons unsalted butter, melted (if using plain croutons)
Instructions
- 1
Caramelize the Onions: In a large skillet, melt 2 tablespoons of unsalted butter and 1 tablespoon of olive oil over medium-low heat. Add the thinly sliced white onions and season with 1/2 teaspoon of kosher salt and 1/4 teaspoon of black pepper. Cook slowly, stirring occasionally, until the onions are deeply golden brown, sweet, and tender, about 30-40 minutes. Set aside.
⏱️ 40 min - 2
Prepare the Green Beans: Bring a large pot of water to a rolling boil. Add 1 teaspoon of kosher salt to the water. Prepare a large bowl with ice and water for an ice bath. Add the trimmed fresh green beans to the boiling water and blanch for 3-4 minutes, until they are crisp-tender and vibrant green. Immediately transfer the blanched green beans to the ice bath to stop the cooking process. Once cooled, drain them thoroughly.
⏱️ 10 min - 3
Make the Mushroom Cream Sauce: In a medium saucepan, melt 3 tablespoons of unsalted butter over medium heat. Add the sliced cremini mushrooms and sauté until they are softened and lightly browned, about 5-7 minutes. Sprinkle in 3 tablespoons of all-purpose flour and cook, stirring constantly, for 1-2 minutes to create a roux. Gradually whisk in 1 1/2 cups of whole milk and 1/2 cup of chicken broth until the sauce is smooth and begins to thicken. Bring to a gentle simmer, stirring frequently, then reduce the heat to low and cook for 5 minutes, or until the sauce coats the back of a spoon. Season with 1/2 teaspoon of kosher salt, 1/4 teaspoon of black pepper, and 1/4 teaspoon of freshly grated nutmeg. Taste and adjust seasoning as needed.
⏱️ 15 min - 4
Preheat Oven and Prepare Dish: Preheat your oven to 375°F. Lightly grease a 9x13 inch baking dish.
⏱️ 5 min•🌡️ 375 - 5
Assemble the Casserole: Spread the drained blanched green beans evenly in the prepared baking dish. Pour the homemade mushroom cream sauce over the green beans, ensuring they are well coated. Distribute the caramelized onions in an even layer over the sauce. Sprinkle the freshly grated Gruyère cheese evenly over the caramelized onions. If your croutons are plain, toss them with 2 tablespoons of melted unsalted butter, then scatter them over the cheese layer.
⏱️ 10 min - 6
Bake the Casserole: Bake the casserole in the preheated oven for 25-30 minutes, or until it is bubbly around the edges, the cheese is melted and slightly golden brown, and the croutons are crispy. If the croutons are browning too quickly, you can loosely tent the casserole with aluminum foil.
⏱️ 30 min•🌡️ 375 - 7
Serve: Remove the casserole from the oven and let it stand for a few minutes before serving to allow the sauce to set slightly. Serve hot.