In a medium bowl, add the powdered sugar. Sprinkle over the top the water, corn syrup and extract. Slowly beat the mixture together with an electric mixer. At first, it will seem like the mixture won't come together, but stay with it. When it begins to clump, gather the mixture in your hands and knead it together. You should have a soft white dough that holds together well.
Next, take two pieces of parchment paper of equal size and dust them with powdered sugar. Place the dough on one piece, dust with more powdered sugar and cover with the other piece of parchment paper. Roll out the mixture to 1/4" thickness. Keep the dough between the two sheets of parchment paper, place it on a small baking sheet and freeze for 30 minutes.
Once 30 minutes has elapsed, peel off the top layer of parchment and cut out as many circles with a 1.5" cookie cutter as you can. When you run out of space, gather up the dough and roll it out again. You should get about 12 circles. Place the circles back on the cookie sheet lined with parchment and freeze solid for at least 1 hour.
When ready to dunk, melt the chocolate and shortening in a double boiler until smooth. Remove from heat and let cool for a few minutes. Now, take the patties out of the freezer and dunk them QUICKLY in the chocolate. Place them back on the sheet and freeze to set. Store in the freezer.
Recipe by Dessert For Two at http://www.dessertfortwo.com/2012/06/peppermint-patties/