To achieve a smooth and creamy texture, use an electric mixer or food processor to make the yam mixture.
Bake the casserole until it's heated and the topping is golden brown. Be cautious not to over bake, as it can dry out the sweet potatoes.
Sweet potato casserole can be made ahead of time. Prepare the casserole, cover it, and refrigerate. You can then bake it when you're ready to serve it.