Fresh Green Bean Casserole
For the casserole:
2 cups thinly sliced shallots
4 tablespoons butter, divided
1 tablespoon olive oil
8 cups (about 1¼ pounds) green beans, trimmed and cut into 1-inch pieces
6 cups cremini and button mushrooms, trimmed and cut into small pieces
2 garlic cloves, minced
3 tablespoons AP flour
1¼ cups chicken broth
1¼ cups heavy cream
½ cup dry white wine
1 tablespoon finely chopped fresh thyme
1 tablespoon finely chopped fresh rosemary
2 tablespoons finely chopped fresh tarragon
1 tablespoon finely chopped fresh sage
1½ teaspoons salt
½ teaspoon pepper
1 cup panko bread crumbs
2 tablespoon unsalted butter, melted
½ cup yellow onion, finely diced
For the topping:
Melt the butter, sauté the onion over low heat until translucent. Raise the heat to medium and toast, stirring often, until golden brown. Set aside.
For the casserole:
Heat oven to 400˚F.
Melt 1 tablespoon butter and olive oil in a large sauté pan over medium-low heat. Add the sliced shallots, stir to evenly coat the shallot in the fat. Cook, covered, stirring occasionally for 20 minutes until the shallots are very soft. Remove the lid and continue cooking over low heat until the shallots are caramelized, about 10-12 minutes.
While the shallots cook, blanch the green beans. Heat a large pot of salted water to a simmer. Prepare a large bowl of ice water. Blanch the green beans until tender but crisp, about 60 seconds. Plunge into the ice water until chilled. Drain well and set aside.
After the shallots are caramelized, transfer to a bowl. In the same pan, heat the remaining butter (you don’t need to wipe out the pan). Raise the heat to medium / medium-high. Add the mushrooms, cook until the liquid is nearly evaporated, about 6-8 minutes. Add the garlic and cook for 1-2 minutes. Stir in the flour and cook for 1 minute. Slowly whisk in the wine then broth and finally the heavy cream, bring to a boil. Cook, stirring occasionally, until sauce has thickened, 4-6 minutes. Stir in the herbs and season with salt and pepper. Toss in the caramelized shallots and green beans. Transfer the mixture to a baking dish. Bake until the sauce is bubbling and green beans are very tender, about 25 minutes.
Remove from oven, top with panko mixture and let cool for 10 minutes.