Green Bean Casserole (from scratch and make-ahead-able)

Source: Mel's Kitchen Cafe

Ingredients:
for the topping:
2 slices hearty sandwich bread, white or wheat, torn into pieces
2 tablespoons unsalted butter, melted (mine was salted so I just left out the salt)
1/4 teaspoon salt
2 cups canned fried onions

for the casserole:
3 tablespoons unsalted butter (mine was salted so I just reduced the salt)
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 (I used two 12 oz packages, so it was only 1.5 lbs - I think this gave it a little bit saucier consistency than if there were more beans, and we like sauce, so it was perfect.)
1/4 cup cornstarch

Directions:
For the topping: Pulse bread, butter, and salt in food processor until coarsely ground.  (I don't have a food processor, so I tried my blender - which I was kinda scared to do, because it's not exactly the best blender in the whole world - I toasted the bread first, then ripped it into pieces and poured the butter over it.  Worked like a charm.) 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 (I used a large sauce pan) 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.  (I didn't need to freeze it for 2 months, though that is a handy thing to know - mine was frozen for just a couple of days, then it made the journey to Utah in the cooler.)

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.

Notes:
I got assigned the "vegetable" for the Blanchard Family Thanksgiving Dinner this year.  I have only been in the family for a couple of Thanksgivings, so I didn't know if there was some sort of traditional vegetable dish that I should make.  I was informed that there wasn't - that I had free reign to find something fabulous - so of course, I turned to Mel's blog, which is my favorite.  Haven't tasted it yet (well, I did taste the sauce and it was pretty dang good), but it looked delicious when I put it in the freezer last night.  Hope the rest of the fam agrees.  :)