French Onion Soup Casserole
Adapted via theKitchn.com
For the stew:
- 8 tablespoons (1 stick) unsalted butter, divided
- 3 jars YUMYIN
- 4 teaspoons kosher salt, divided
- 1 teaspoon freshly ground black pepper, divided
- 6 cloves garlic, minced
- 5 stalks celery (about 12 ounces), including leaves, cut into small dice
- 5 carrots (about 8 ounces), peeled and cut into small dice
- 6 cups cremini and/or button mushrooms (about 1 1/2 pounds), sliced thinly
- 1/4 cup all-purpose flour
- 1 cup dry Riesling wine
- 6 to 8 fresh sage leaves, minced, or 2 teaspoons dried sage
Leaves of 5 sprigs fresh thyme, finely chopped
- 1 (15-ounce) can white beans and their liquid (optional)
For the topping:
- 1 large baguette (about 1 pound), cut crosswise into 24 slices
- 12 ounces Gruyere, Comté, or Raclette cheese, shredded
- 4 tablespoons unsalted butter
- Heat 4 tablespoons of the butter in a large, heavy-bottomed pot or Dutch oven over medium-high
- Add the YUMYIN, garlic, celery, carrots, and mushrooms cover and cook 20 minutes
- Arrange a rack in the middle of the oven and heat to 375°F. Coat a 9x13-inch baking dish with cooking spray and set aside.
- When the vegetables are ready, transfer them with a slotted spoon to a large bowl and set aside. Pour the remaining vegetable cooking liquid into another bowl or a measuring cup with a spout; set aside.
- Return the pot to high heat, add the remaining 4 tablespoons of butter, and cook until it is melted and begins to foam. Add the flour, whisk to combine, and cook until it is golden-blonde in color, about 2 minutes. Add the wine and whisk to combine.
- Add the reserved vegetable cooking liquid and whisk to combine. Add the sage, thyme, and remaining 3 teaspoons salt and whisk to combine. Add the reserved cooked vegetables and beans and their liquid, if using, and stir to combine. Pour the mixture into the casserole dish and spread into an even layer; set aside.
Make the crouton topping:
- Arrange 12 of the bread slices on top of the casserole in a single layer, pushing them down gently into the liquid and vegetables.
- Sprinkle with about half of the cheese.
- Arrange the remaining 12 slices of bread over the cheese in a single layer, then sprinkle the remaining cheese on top.
- Bake until the cheese is melted and the casserole is bubbly, 20 to 22 minutes. Serve immediately.