Fresh Green Bean Casserole

I discovered this recipe a few years ago and have been serving it for the holidays ever since.  Sorry Campbell's Condensed Mushroom Soup...I can never go back!

Topping Ingredients:
4 slices white bread, each slices torn into quarters
2 tablespoons unsalted butter, softened
¼ teaspoon salt
1/8 teaspoon ground black pepper
3 cups canned fried onions (about 6 ounces)
Beans and Sauce Ingredients: 2 tablespoons salt
2 pounds green beans, ends trimmed, and halved
3 tablespoons unsalted butter
1 pound white button mushrooms, stems removed, wiped clean and broken into ½-inch pieces
3 cloves garlic, minced (about 1 tablespoon)
Salt and pepper, to taste
3 tablespoons all-purpose flour
1½ cups chicken broth
1½ cups heavy cream

For the Topping:

Pulse bread, butter, salt and pepper in food processor until mixture resembles coarse crumbs, about ten 1-second pulses. Transfer to a large bowl and toss with onions; set aside.
For the Beans and Sauce:
Adjust oven rack to middle position and heat oven to 425 degrees F. Fill a large bowl with ice water. Bring 4 quarts of water to a boil in a large pot or Dutch oven. Add 2 tablespoons salt and beans. Cook beans until bright green and crisp-tender, about 6 minutes. Drain beans in colander and plunge immediately into ice water to stop cooking. Spread beans on paper towel-lined baking sheet to drain. Add butter to now-empty pot and melt over medium-high heat until foaming subsides. Add mushrooms, garlic, ¾ teaspoon salt, and 1/8 teaspoon pepper; cook until mushrooms release moisture and liquid evaporates, about 6 minutes. Add flour and cook for 1 minute, stirring constantly. Stir in broth and bring to simmer, stirring constantly. Add cream, reduce heat to medium, and simmer until sauce is thickened and reduced to 3½ cups, about 12 minutes. Season with salt and pepper to taste.
Add green beans to sauce and stir until evenly coated. Arrange in an even layer in 3-quart (or 9×13-inch) baking dish. Sprinkle with topping and bake until top is golden brown and sauce is bubbling around edges, about 15 minutes. Serve immediately.