Description
A creamy baked casserole of blanched green beans and browned crimini mushrooms in a Parmesan béchamel, topped with crispy fried onions.
Ingredients
Scale
- 2 lb. fresh 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
- 1? cups whole milk
- 1 cup heavy cream
- 4 garlic cloves, finely grated
- ? cup grated Parmesan
- Freshly ground black pepper
- ? cup French?s fried onions
Instructions
- Place rack in middle of oven; preheat oven to 375?F (190?C).
- Working in batches, cook the green beans in a large pot of boiling salted water until bright green and halfway to tenderness, about 3 minutes per batch; drain, let cool, and trim stem ends.
- Heat 1 Tbsp. extra-virgin olive oil in a large skillet over medium-high heat; cook ? lb. sliced crimini mushrooms without stirring until golden brown underneath, about 2 minutes, then 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 the pan; cook, tossing occasionally, until the butter browns and mushrooms are dark brown and very tender, about 4 minutes longer; season with kosher salt and transfer to a plate.
- Repeat the mushroom browning with the remaining 2 Tbsp. unsalted butter, remaining 1 Tbsp. extra-virgin olive oil, remaining ? lb. sliced crimini mushrooms, 2 large thyme sprigs, and salt.
- Melt the remaining 2 Tbsp. unsalted butter in a large saucepan over medium-low heat; whisk in 2 Tbsp. all-purpose flour and cook, whisking occasionally, until the roux is golden brown and smells mildly nutty, about 4 minutes.
- Whisk in 1? cups whole milk and 1 cup heavy cream; increase heat and bring to a simmer, whisking often, and cook until the b?chamel is thick and bubbling, about 5 minutes; remove from heat and whisk in 4 finely grated garlic cloves and ? cup grated Parmesan; season with salt and freshly ground black pepper.
- Arrange the green beans and mushrooms in a 2-qt. baking dish and pour the sauce over the mixture; cover tightly with foil and bake until the sauce is bubbling, 25?30 minutes, then uncover and continue to bake until the casserole is lightly browned on top and around the edges, 15?20 minutes longer.
- Top with ? cup French?s fried onions and continue to bake just until the onions are slightly darker and fragrant, about 3 minutes; let sit 10 minutes to set before serving.
- Prep Time: 25 mins
- Cook Time: 1 hr 5 mins