This is a VERY sweet dessert and should be eatten in moderation. To store this, line a tin or container with wax paper and place one layer of candy down. Then add more wax paper to the top of that layer and continue until full. Store in the fridge or a cool dry place.
In a large bowl, mix mashed potato and vanilla extract. Slowly stir in Confection sugar. Be aware that the potatoes will become very runny when you first start.
The mixture will form a dough when you have added enough confection sugar. Reserve a little bit of the sugar for dusting. When you have a ball of dough formed, dust a clean surface and turn dough out onto that surface. You will want to roll out the dough to about 1/2 inch thick.
With a large spoon or spatula, spread peanut butter on the top of the dough mixture but keep back about 1/2 and inch from the edge. Start at one end and roll the dough and peanut butter mix like a cake roll. Place on a sheet pan and put in the refridgerator for about an hour. Remove and slice into pieces about 1/2 and inch thick.