This post from Kriss Harvey, one of my chocolate gods, shows the process. He uses this technique when he wants to cap a bonbon that has a liquid filling that can't be capped the traditional way (because the chocolate would displace the filling). If you're using a traditional filling like a ganache, gianduja. praline or even a firmer caramel that can support the weight of the chocolate, there owuld be no reaosn to use this method over the regular way of capping your bonbons. There is also capping the bon bons with an acetate sheet or transfer sheet as @RWood described, but it doesn't sound like that's what you're talking about (but just in case, take a looka t the second video, also from Kriss Harvey).