In a large bowl, blend the mashed potatoes, softened butter, and 1 cup of the confectioners' sugar using an electric mixer until well combined.

Gradually add in the remaining confectioners' sugar, 1 cup at a time, mixing thoroughly after each addition. Once you've incorporated around 6 cups, check the dough's consistency. It should be firm enough to mold and roll. If too soft, continue adding more sugar until the desired texture is achieved.

Mix in the vanilla extract until fully incorporated.

Cover and refrigerate the dough for 30-60 minutes to firm up. If chilled for too long and becomes overly stiff, let it sit at room temperature for 10-15 minutes to become pliable again.

Divide the chilled dough into two equal portions. Generously dust a clean surface with confectioners' sugar. Roll out one portion into a ¼ inch thick rectangle, approximately 8x12 inches. If too sticky, dust with more sugar as needed.

Spread an even layer of creamy peanut butter over the dough rectangle, leaving a small border around the edges.

Starting from a long side, carefully roll up the dough into a tight log, sealing the seam.

Using a sharp knife, slice the log into ¼ - ½ inch thick pinwheels.

Repeat steps 5-8 with the remaining dough portion.

Serve the potato candy pinwheels fresh or store them in an airtight container in the fridge for up to a week.