TIP: In this episode, Jo makes the green bean casserole in a 2-quart baking dish. The recipe method here (and in "Magnolia Table, Volume 2 Cookbook") calls for a 9 x 11-inch baking dish. You can use either type of dish to achieve the same green bean casserole.
a deep-fry thermometer
a deep-fry thermometer
1 large yellow onion, thinly sliced
1/2 cup buttermilk
1 cup cornstarch
1 teaspoon seasoned salt
Canola oil, for deep-frying
5 tablespoons unsalted butter, melted
1 tablespoon plus 1 teaspoon kosher salt
2 pounds green beans, ends snapped
Two 8-ounce packages sliced portobello mushrooms
1 teaspoon freshly ground black pepper
2 garlic cloves, minced
1/3 cup all-purpose flour
3/4 cup chicken broth
1 3/4 cups heavy cream
Preheat the oven to 375°F. Lightly grease a 9 x 11-inch baking dish.
In a large bowl, dip onion slices in buttermilk. Combine the dipped onion slices, cornstarch, and seasoned salt and toss until the onions are well coated.
Pour 3 inches of oil into a deep medium saucepan. Have ready a wire rack lined with paper towels to use for draining. Heat the oil to 350°F on a deep-fry thermometer.
Working in batches, use a slotted spoon to lower half the onions into the hot oil. Cook, stirring occasionally, until golden, 2 to 3 minutes. Use a slotted spoon to remove the onions to the paper towel-lined rack. Repeat to fry the remaining onions. Set aside.
Set up a large bowl of ice and water. Bring a large pot of water with 1 tablespoon of the salt to a boil over medium-high heat. Add the green beans and cook until crisp-tender, about 6 minutes. Using tongs, carefully remove the green beans to the ice water to stop the cooking process. Cool in the ice water for 1 to 2 minutes, then drain the beans. Set aside.
In a large skillet, heat the remaining 4 tablespoons butter over medium-high heat. Add the mushrooms and cook, stirring frequently, until golden brown, 2 to 3 minutes. Add the remaining 1 teaspoon salt, the pepper and garlic and stir to combine.
Sprinkle the flour over the mushrooms and stir to combine well. Slowly whisk in the chicken broth, bring to a simmer, and cook until well incorporated, about 2 minutes. Reduce the heat to medium and slowly whisk in the cream, stirring until the sauce thickens, 4 to 6 minutes. Remove from the heat and stir in the green beans and then pour into the prepared baking dish.
Transfer to the oven and bake until bubbling, 15 to 20 minutes. Top with the fried onions and serve.
Store in an airtight container in the refrigerator for up to 2 days.