Start off by boiling a small potato until tender. Mash the russet potato in a large bowl until nice and smooth. Add the vanilla extract and salt and slowly work in the confectioners' sugar using an electric mixer until a dough forms. It should almost feel like Play-doh.
Move the mixture to a flat surface which has been sprinkled with powdered sugar. Using a rolling pin, roll dough into a 1/4 inch thick rectangle. Spread the creamy peanut butter on the potato mixture and roll into a jelly roll shape starting from the long side. Wrap in parchment paper or wax paper and chill for one hour.
Remove the log from the fridge and slice into 1/2-inch pinwheels. Store the candy in an airtight container for up to a week.