I prefer fresh for their flavor and texture. However, frozen sweet potatoes can be a quick and easy option. Frozen sweet potatoes come already peeled and usually in small cubes. Some can even be steamed right in the bag. They can also be cooked on the stove top or even in the oven. Frozen sweet potatoes also bake quickly on a sheet tray with parchment paper. Just be sure to keep an eye on them and pull the sweet potato cubes out as soon as they are soft. Don't wait until they have browned or caramelized on the outside as they won't mash as smoothly. I do not recommend canned sweet potatoes in this recipe. They are packed in sweet syrup which will alter the flavor and texture of your sweet potato casserole recipe.