In a bowl, blend the mashed potatoes and vanilla. With a wooden spoon gradually add the icing sugar to form a soft dough, but one that holds together well.
Sprinkle a work surface with icing sugar. Knead the dough a few minutes to give it the texture of pie dough. On parchment paper, roll out the dough into a 35 x 20-cm (14 x 8-inch) rectangle.
Heat the peanut butter in the microwave for a few seconds and spread over the dough. Holding the paper, roll the dough into a cylinder about 35-cm (14-inch) long. Slide onto a baking sheet and refrigerate for about 1 hour. Cut into twenty 1-cm (1/2-inch) slices.
Store in an airtight container.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.