Make Ahead Green Bean Casserole

I can't remember which blog I got this from, it's one of those listed on my side bar.

Topping:
2 slices hearty sandwich bread, white or wheat, torn into pieces
2 tablespoons unsalted butter , melted
1/4 teaspoon salt
2 cups canned fried onions

Casserole:
3 tablespoons unsalted butter
10 ounces white mushrooms , sliced thin
1 teaspoon salt
1/2 teaspoon pepper
6 garlic cloves , minced
1/2 teaspoon dried thyme
1/4 cup all-purpose flour
1 3/4 cups low-sodium chicken broth
1 1/2 cups heavy cream
2 pounds fresh green beans, trimmed and cut into 1-inch pieces
1/4 cup cornstarch

For the topping: Pulse bread, butter, and salt in food processor until coarsely ground. Combine bread mixture and canned fried onions in a bowl, transfer to a zipper-lock freezer bag, and freeze.

For the casserole: Melt the butter in a large 12-inch skillet over medium heat. Add the mushrooms, salt, and pepper and cook until the mushrooms release their liquid, about 5 minutes. Increase the heat to medium-high and cook until all the liquid has evaporated, about 5 minutes. Add the garlic and thyme and cook until fragrant, about 30 seconds. Stir in the flour and cook until golden, stirring, about 1 minute. Slowly whisk in broth and cream and bring the mixture to a boil. Reduce the heat to medium and simmer, stirring occasionally, until the sauce has thickened, about 10 minutes.

In a large bowl, toss the green beans with the cornstarch until the beans are evenly coated. Transfer the beans to a 9X13-inch baking dish. Pour the warm mushroom mixture evenly over the beans. Let the casserole cool completely on the counter. Once cooled, cover with a layer of plastic wrap and then a layer of foil. Freeze for up to 2 months.
When ready to bake, adjust oven rack to the middle position and heat the oven to 400 degrees. Remove the layer of plastic wrap from the baking dish and replace the foil. Bake, covered, until the sauce is bubbling and the beans are tender, about 80 minutes, stirring the beans thoroughly after 50 minutes. Remove the foil and spread the frozen topping mixture over the beans. Bake until golden brown, about 8-10 minutes. Serve.

I did not not freeze this, I just followed the directions and then baked it for about an hour- just watch it.
We had this for Thanksgiving dinner and I forgot to get ratings from people.  It was good and I have never been a fan of green bean casserole.  My brother, Kevin really liked it.