Cook a small potato with the skin on it. (Boil it until done) 
Remove peeling while hot. Mash with a fork . Add vanilla.
This will make the potato mixture real runny. Add confectioner's sugar. A little at a time until you reach the consistency of a ball of dough. 
Use the confectioners sugar like you would flour. Sprinkle on flat surface. Roll out the dough mixture with a rolling pin. You want the dough to be about 1/4 inch thick.

Spread a thin layer of peanut butter on it. Roll it up like a jelly-roll and slice.
Keep covered and refrigerated.