That is SO funny about your cat sitting on chocolate and especially funny that he sits on the cakes.
My dog, Haley, does something similar with chocolate. I found a warm hershey kiss in bed and a warm m&m another time. She gets them and puts them under her arms/chest to guard them. The first time I saw the Hershey kiss, I panicked. Then I realized that she doesn't eat it, she just "nests" on it.
Maybe it's their way of trying to keep us from eating sugary food that is bad for us!!