Green Bean Casserole with Fresh Beans

1 . Stage

Preheat the oven to 350 degrees F (175 degrees C). Fill a large bowl with ice and cold water.

2 . Stage

Bring a large pot of lightly salted water to a boil. Add green beans and cook, uncovered, until crisp-tender, about 6 minutes. Drain in a colander and immediately immerse in ice water for several minutes to stop the cooking process. Drain and transfer to a large bowl

3 . Stage

Heat 3 tablespoons butter in a large skillet over medium-high heat. Saute onion in the hot butter until translucent, about 5 minutes. Add mushrooms and garlic; saute until mushrooms are just cooked through, about 5 minutes. Stir into green beans.

4 . Stage

Place remaining 5 tablespoons butter in a 2-quart, microwave-safe bowl. Microwave on high power in 30 second intervals, until melted.

5 . Stage

Add flour to melted butter and whisk until smooth. Add sea salt and pepper, then add 1 cup of milk; whisk until mixed together. Microwave for 2 minutes. Add the next cup of milk, whisking until smooth; microwave for 2 minutes. The roux mixture should thicken between additions, less so as each cup is added. Add remaining cup of milk; microwave for 2 minutes more, and then whisk.

6 . Stage

Pour the green bean mixture into a 9x13-inch baking pan. Add the thickened roux and combine. Add salt and pepper if desired.

7 . Stage

Bake in the preheated oven until warm and bubbly, about 30 minutes. Top with crispy fried onions and return to the oven for 5 minutes.