If you use a silicone madeleine pan, the chocolate shell can easily be popped out when the chocolate is set just by pushing against the silicone. If you use a metal pan, you will need to freeze the pan to make sure the chocolate has hardened completely before releasing them. Hold the pan vertically and use your fingers to push down on the top edge of each madeleine. Push gently but firmly until the madeleine slides out. If the madeleines aren't popping off easily, freeze for another 5 minutes and try again.