Combine the cream and milk in a large saucepot over medium heat. Bring the liquid to an almost boil.
together the yolks, sugar and salt in a separate bowl. Gently add about 2 cups of the hot liquid, whisking until smooth. Add the egg mixture to the remaining cream/milk
mixture, whisking until smooth. Remove from the heat.
In a separate container, combine the vanilla extract
and the drained sweet potato. Using either a hand stick blender
or a blender, puree until smooth.
Whisk the sweet potato puree into the egg mixture. Strain through a mesh strainer
to remove any large chunks. Cool slightly over an ice bath, stirring constantly. You want it to be about room temperature.
Add the mixture to the ice cream machine, and make according to the machine's instructions.
Once the ice cream is complete, fold in swirls of the marshmallow
creme, and freeze to set. Yield: about 2 quarts.