Ok for Nathaniel's cake I tried to do this.
But cheat and use a cake mix LOL. It worked, sort of... When I have flour again I will be trying the actual cake.
Then for the frosting... Now Nathaniel wanted a pokeball cake, but I had issues finding red icing so I surprised him with this....
Then just to add to it make it look more like a fossil I crushed up some graham crackers to be the dirt... I'm really proud of myself! I'm not normally very good at things like this but I think it turned out good.
This is what it looked like when we cut it.. not quite as clear as I wanted it.. but pretty cool!