Green Bean Casserole - Make Ahead

This recipe can be assembled, baked and served right away or assembled and frozen for up to 2 months.

Prep Time20

Cook Time1 20

Total Time1 40

Course: Side Dish

Cuisine: American

Keyword: casserole, vegetables

Servings: people

Calories: 208kcal

Author: Sally Humeniuk

3 Tablespoons unsalted butter
10 ounces white mushrooms, sliced thin
1 teaspoon salt
½ teaspoon pepper
6 garlic cloves, minced
½ teaspoons dried thyme
¼ cup unbleached all-purpose flour
½ cup white wine or cooking wine
1 ½ cups low-sodium chicken broth
1 ½ cups heavy cream
2 pounds green beans, trimmed and cut into 1-inch pieces (frozen beans works, don't use canned)
¼ cup cornstarch

Pulse 2 slices bread, 2 Tablespoons butter and ¼ teaspoon salt in a food processor until coarsely ground, about 10 pulses. Combine the bread mixture and 2 cups onions in a bowl, transfer to a large zip-lock freezer bag, and freeze for up to 2 months. If making the casserole to cook the same day as prep, place the topping in refrigerator until needed.

Melt 3 Tablespoons butter in a large skillet over medium heat. Add 10 ounces mushrooms, 1 teaspoon salt and ½ teaspoon pepper and cook until the mushrooms release their liquid, about 5 minutes. Increase the heat to medium-high and cook until the liquid has evaporated, about 5 minutes. Add 6 minced garlic and ½ teaspoon thyme and cook until fragrant, about 30 seconds. Stir in ¼ cup flour and cook until golden, about 1 minute. Slowly whisk in ½ cup wine, 1 ½ cups broth and 1 ½ cups cream and bring to a boil. Reduce the heat to medium and simmer, stirring occasionally, until the sauce is thickened, about 10 minutes.
Toss 2 pounds green beans with ¼ cup cornstarch in a large bowl and transfer to a 13 by 9-inch baking dish. Pour the warm mushroom mixture evenly over the beans (do not mix). Let cool completely, cover with plastic wrap, cover with foil, and freeze for up to 2 months.

Remove the casserole from the freezer and take away the plastic from the baking dish and replace the foil. Adjust an oven rack to the middle position and heat the oven to 400 degrees. Bake until the sauce is bubbling and the beans are tender, about 80 minutes, stirring the beans thoroughly and adding almonds or water chestnuts after about 50 minutes. Remove the foil and spread the topping mixture over the beans. Bake until golden brown, about 8 minutes. Serve.

Once the mushroom mixture has been poured over the beans, (do not mix in) cover with aluminum foil and bake in a 350F degree oven for 60 minutes. Remove foil, stir the beans and sauce thoroughly, add almonds or water chestnuts. Then sprinkle fried onion mixture over top and bake uncovered an additional 10 minutes. Ready to serve!

If you're wanting a gluten-free option, use gluten-free bread where the recipe calls for white sandwich bread and instead of flour in the sauce, use cornstarch, starting with only 2 tablespoons. Cornstarch and flour are not substituted for each other one to one. You will use a lot less cornstarch to get the same consistency as you need using flour.