The way my wife does it is by boiling them, peeling them, cutting them into cubes, then putting them in a glass tray, putting cinnamon sugar, butter, and marshmallows on top, then baking them.
In our family, it's always been served as a side dish, not a desert, but sweet potatoes mixed with a ton of butter and brown sugar, and then topped with marshmallows and baked... that usually was enough for me to satisfy any need for desert. I don't know how any of us avoided emerging from childhood without diabetes.