A friend of my dad's requested a chocolate construction site cake for his son's birthday. He provided the toy trucks, and I puzzled out how I was going to make this cake. I knew I could use crushed Oreos for a soil effect and chocolate buttercream for mud, but how was I going to get mounds of 'dug up' chocolate soil to stay in place when the cake needed to be transported?
I solved the logistical problem by creating cake pop dough from the offcuts from levelling the cake, binding the cake crumbs together with a bit of extra chocolate buttercream. I shaped them and rolled them in crushed Oreos. Voilà! Instant mounds of soil that won't scatter all over the board when the cake is moved. This also solved the problem of cleanup of the toy vehicles afterwards: rather than having a load of biscuit crumbs stuck in the cracks of the dump truck for example, the 'pile of dirt' is just a lump of cake rolled in crumbs that can just be lifted out.