Peel and boil the potato (like you would for mashed potatoes). When it is soft and fully cooked, take it from the water and put it in a mixing bowl. Mash it up till there are no chunks.
Add one capful of pure vanilla extract (no more!) and mix. Consistency will get really thin. Add 1-2 cups powdered sugar and continue mixing. Continue adding the powdered sugar/mixing until the consistency is like that of cookie dough. This will take most if not all of the bag of powdered sugar.
When the consistency is right, lay down some flour on a flat surface and roll your potato candy out to 3/8" or 1/2" thickness. Add a thin layer of peanut butter (1/8" to 1/4").
Roll potato candy (with the peanut butter on top) from one end to the other. This makes a long roll that looks kind of like a spiral from the side. Cut into pieces about and inch thick.
Serve and enjoy!