Without a doubt, fresh green beans are what you need for the best green bean casserole. Canned green beans, while a convenient time-saver, become mushy and tasteless, which can lead to a soggy casserole. Blanched fresh green beans are tender but crisp, the perfect texture! If you are short on time and don’t want to trim and cut fresh green beans, simply buy a bag of frozen green beans. Thaw them out and blanch them as instructed in the recipe.