Make-Ahead Green Bean Casserole is made with fresh green beans and a homemade cream-of-mushroom soup that is delicious enough to be eaten on its own. It can be made in advance up to (but not including) the topping. It freezes well, so how far in advance you want to make the dish is up to you. If you’re making this for Thanksgiving, simply pop it in the oven when the turkey comes out and let it bake while the bird rests.