I have made chocolate clay and used it. It is easy to make. I recently watched some tutorials where the decorator used part chocolate clay and part fondant. This gives the chocolate clay a little more stretch like fondant, but also keeps the long working time that is nice with chocolate clay -- it doesn't dry like fondant. It is very nice because the heat of your hand makes it easy to shape and smooth it. Hot hands can be a challenge though, making the chocolate clay soften too much.