Best Ever Green Bean Casserole

I found this recipe off the Food Network. It's Alton Brown recipe for The Best Ever Green Bean Casserole. We loved it! Much better than the canned stuff and pretty easy to do. However, I did try to make my own onions like the recipe shows but I only cooked them for half the time and they were all burnt and nasty. I then looked up the reviews on this recipe and everyone had problems with the onions. So we did like many of them, just make the bean and sauce and added the French's onions. It was very yummy. Will be making this instead of the canned stuff from now on.

For beans and sauce:

• 2 tablespoons plus 1 teaspoon kosher salt, divided
• 1 pound fresh green beans, rinsed, trimmed and halved
• 2 tablespoons unsalted butter
• 12 ounces mushrooms, trimmed and cut into 1/2-inch pieces
• 1/2 teaspoon freshly ground black pepper
• 2 cloves garlic, minced
• 1/4 teaspoon freshly ground nutmeg
• 2 tablespoons all-purpose flour
• 1 cup chicken broth
• 1 cup half-and-half

Directions

For beans. Bring a gallon of water and 2 tablespoons of salt to a boil in an 8-quart saucepan. Add the beans and blanch for 5 minutes. Drain in a colander and immediately plunge the beans into a large bowl of ice water to stop the cooking. Drain and set aside.

Melt the butter in a 12-inch cast iron skillet set over medium-high heat. Add the mushrooms, 1 teaspoon salt and pepper and cook, stirring occasionally, until the mushrooms begin to give up some of their liquid, approximately 4 to 5 minutes. Add the garlic and nutmeg and continue to cook for another 1 to 2 minutes. Sprinkle the flour over the mixture and stir to combine. Cook for 1 minute. Add the broth and simmer for 1 minute. Decrease the heat to medium-low and add the half-and-half. Cook until the mixture thickens, stirring occasionally, approximately 6 to 8 minutes.

Remove from the heat and stir in 1/4 of the onions and all of the green beans. Top with the remaining onions. Place into the oven and bake until bubbly, approximately 15 minutes. Remove and serve immediately.