This is an 8-inch round cake frosted in buttercream. The star, cacti, and barbed wire border are made from modeling chocolate. To make the star, I rolled out the modeling chocolate, cut out a star, and then rolled a cutter gently along the spots where I wanted to fold it (not cutting all the way through, but enough to make a good fold). Then I just lifted and pushed until I had the right dimension. I let it rest on a blob of modeling chocolate to harden, but I didn't put anything under it on the cake, since it was nice and hard.