1. Add the peanut butter, butter, powdered sugar, and vanilla to the bowl of a stand mixer. Beat until combined. Roll the dough into 1 inch balls and place on a parchment-lined cookie sheet. 2. Insert a cinnamon stick into the center of each dough ball. Drizzle chocolate around the cinnamon stick to look like a stem. Sprinkle with cinnamon sugar. Transfer to the freezer and chill in freezer until firm, about 30 minutes. Once chilled, use the pumpkins to decorate the cake.