01 - 
                In a large bowl, beat the mashed potato, milk, vanilla, and salt with an electric mixer on medium speed for 2 minutes.
              
              
              
                02 - 
                Gradually mix in powdered sugar, 1 cup at a time, until a dough has formed. Add more sugar in 1 tablespoon increments if necessary, ensuring the dough is thick and slightly thicker than cookie dough.
              
              
              
                03 - 
                Form the dough into a ball and dust it with powdered sugar. On a sheet of wax or parchment paper, roll the dough into a rectangle approximately 1/8-inch thick. Trim the rectangle to 10x12 inches.
              
              
              
                04 - 
                Generously sprinkle powdered sugar over the surface of the dough. Place another sheet of parchment paper on top, invert the rectangle, and carefully remove the original parchment sheet.
              
              
              
                05 - 
                Spread the peanut butter evenly over the surface of the dough.
              
              
              
                06 - 
                Tightly roll the dough from the long side to the long side using the parchment paper to guide it, forming a jelly-roll style log.
              
              
              
                07 - 
                Wrap the rolled dough in parchment paper and freeze for 1 hour. Cut the roll into 1/4-inch thick slices before serving.
              
              
              
                08 - 
                Store leftover candy in an airtight container in the refrigerator.