I've now seen several recipes for mirror cakes -- the cakes you sometimes see in fancy bakeries that look shiny. (Think PVC vinyl.) Here's a short video that explains the concept. https://www.youtube.com/watch?v=FAXoOhbrflU There are many other, with tutorials.
I wonder if this recipe might have some WAM use. The problem likely is going to be the temperature of the liquid when it is pourable. It has to be low enough not to burn the skin. But what a lovely picture it would make. And unlike paints, it would be edible. Plus, the ingredients seem inexpensive enough.
Being lazy, and having inquisitive young ones in the house, I won't be experimenting, but maybe others would.