Making chocolate ganache for frosting cakes is a great idea. Use 70% chocolate for this, and melt down about 1 cup of it in a microwave, at low power with 20 second bursts, stirring after each session. It will take about 2 minutes for the chocolate to melt. It is a good idea to keep the chocolate at about 110 degrees temperature. At that point, keep 1 cup of hot cream ready. Add the cream very slowly into the chocolate in small amounts till the chocolate is mixed with the cream and forms an emulsion.
You can use other kinds of chocolate as well, and you would need to mix it really hard to have a shiny and glossy ganache. You can glaze a cake right away with it, or you can let it cool at room temperature for 2 hours and then frost cupcakes with it. You can also put it in a whipped cream dispenser, add nitrogen to it, and put in a batch of aerated chocolate frosting over the cake. This is a fantastic recipe that is both decadent and simple.