Mix condensed milk and peppermint extract in a large bowl. Gradually add confectioners' sugar to make a stiff, non-sticky dough.
3
Peppermint mixture into 1-inch balls on waxed paper; flatten into patties with fingers. Patties should dry at room temperature for two hours, turning once.
4
In a medium pot, melt the chocolate and shortening over low heat. Take the pan off the heat and stir in the vanilla. Place one patty at a time on the tines of a fork and dip it into the chocolate mixture.
5
Shake off any extra chocolate by tapping the fork on the edge of the pan. Put the patties back on the waxed paper and put them in the fridge until they are set.