In a mixing bowl, combine the powdered sugar, butter, peppermint extract, and cream. On medium-high, beat with a paddle attachment (mixture will be crumbly at first). Turn mixer on high and beat until it becomes creamy and smooth. Candy should be soft, but not sticky. If it is too sticky, add more powdered sugar, a little at a time, until the consistency is that of Play-Doh. Roll out a long piece of plastic wrap. Scoop out mixture onto the wrap and form it into a long thin roll about 1 ½-inch in diameter (this will be the size of the inside of your peppermint patty). Roll it up tightly in the plastic wrap and twist or tie off the ends (Jan’s Note: I divided the mixture up into two logs and wrapped each in plastic wrap to keep one log chilled while working with the other (tip: to keep your candy round, cut a slit all the way down an old cardboard paper towel tube, and put the candy inside, which will help keep the bottom from flattening as it sits in the refrigerator)). Chill the candy until it is very firm – at least 1 hour. Prepare a sheet pan lined with parchment paper and place it in the refrigerator to chill. When the candy has hardened, remove from the plastic wrap, and, using a sharp knife, slice off rounds about ¼-inch thick. Melt the dipping chocolate in the microwave in 30-second intervals, stirring to prevent overheating. Using a fork or dipping tool, dip a patty into the melted chocolate, coating completely. Let the excess coating drip back into the bowl. Set the candy on a chilled, parchment-lined baking sheet, and repeat with the rest of the candy slices. Immediately refrigerate to harden. Store in an airtight container in fridge or at room temperature.