BA's Best Green Bean Casserole

• portions: 8 servings

Ingrédients

2 lb. green beans

Kosher salt

2 Tbsp. extra-virgin olive oil, divided

1 lb. crimini mushrooms, sliced, divided

6 Tbsp. unsalted butter, divided

4 large sprigs thyme, divided

2 Tbsp. all-purpose flour

1¼ cups whole milk

1 cup heavy cream

4 garlic cloves, finely grated

½ cup grated Parmesan

Freshly ground black pepper

¾ cup French’s fried onions

Instructions

Place rack in middle of oven; preheat oven to 375°. Working in batches, cook 2 lb. green beans in a large pot of boiling salted water until bright green and halfway to tenderness, about 3 minutes per batch. Drain and let cool; trim stem ends.

Heat 1 Tbsp. extra-virgin olive oil in a large skillet over medium-high. Cook ½ lb. crimini mushrooms, sliced, without stirring, until golden brown underneath, about 2 minutes. Toss and continue to cook, tossing occasionally, until browned on both sides, about 3 minutes more. Add 2 Tbsp. unsalted butter and 2 large thyme sprigs to pan. Cook, tossing occasionally, until butter browns and mushrooms are dark brown and very tender, about 4 minutes longer. Season with kosher salt and transfer to a plate. Repeat with 2 Tbsp. unsalted butter, salt, and remaining 1 Tbsp. extra-virgin olive oil, ½ lb. crimini mushrooms, sliced, and 2 large thyme sprigs.

Melt remaining 2 Tbsp. unsalted butter in a large saucepan over medium-low. Whisk in 2 Tbsp. all-purpose flour and cook, whisking occasionally, until roux is golden brown and smells mildly nutty, about 4 minutes. Whisk in 1¼ cups whole milk and 1 cup heavy cream. Increase heat and bring to a simmer, whisking often, and cook until béchamel sauce is thick and bubbling, about 5 minutes. Remove from heat and whisk in 4 garlic cloves, finely grated, and ½ cup grated Parmesan; season with salt and freshly ground pepper.

Arrange green beans and mushrooms in a 2-qt. baking dish. Pour sauce over bean mixture (it may not look like enough, but it will get saucier as it bakes). Cover tightly with foil and bake until sauce is bubbling, 25–30 minutes. Uncover and continue to bake until casserole is lightly browned on top and around the edges, 15–20 minutes longer. Top with ¾ cup French’s fried onions and continue to bake just until onions are slightly darker and fragrant, about 3 minutes. Let sit 10 minutes to set before serving. Editor’s note: This recipe was first printed in November 2016. Head this way for more of our best Thanksgiving dinner recipes →