In a bowl, stir together the sugar, condensed milk and extract until it forms a smooth, soft dough. Keep the dough covered in plastic wrap so it won't dry out. Dust your board with powdered sugar and roll the dough out until it is about 1/8-inch thick. Cut into 1 1/2-inch rounds or other shapes, re-rolling the dough as needed. Put the chocolate into a heatproof bowl and set it over a pot of simmering water to melt it. Alternately, put the bowl into the microwave and cook in 30 second intervals, stirring each time. Dip the peppermint creams into the chocolate until they are half covered. Lay them onto a parchment or wax paper-covered baking sheet until set. Store the creams between sheets of parchment or wax paper, dusted with powdered sugar, in an airtight container. They will keep for 2 to 3 days.