Place potato in a small pan and cover with water. Cook until very tender. Drain and place in a large bowl.
Use a hand mixer to beat the potato until it is lump-free.
Add 4 cups of powdered sugar and beat until mixed well.
Continue to mix powdered sugar in 1 cup at a time until thick. (It should have the consistency of putty or cookie dough.
Place on a large piece of waxed paper that has been lightly coated with powdered sugar. Sprinkle some more powdered sugar on top.
Roll potato mixture out into a 1/4-inch thick rectangle.
Spread evenly with peanut butter.
Starting at a long side, roll up tightly like you would cinnamon rolls. Wrap in wax paper, cut in half and place both pieces in a large ziptop bag.
Refrigerate at least 30 minutes or until ready to serve.
Remove wax paper and cut into 3/4-inch slices.