The two names are often used as different ways to refer to the same general dish of baked potatoes, spices, sweetener, and other seasonings or add-ins (nuts, butter, marshmallows, etc.). So, this recipe can be referred to as either a sweet potato casserole or soufflé. The official name is soufflé, however, since it rises and gets fluffy while baking as would a traditional soufflé recipe.