How the heck does this work?

Okay, I'm at my friend Patricia's house, and her daughter has a Disney Princess Cool-Bake Magic Oven. It's like an E-Z Bake Oven, but instead of using a lightbulb to cook the cakes, it using ice cubes. You put the ice cubes in a tray at the bottom of the plastic oven, you put the tray of batter-y stuff above the above, and in 12 minutes the cakes rise and are done. I've Googled this online - we're mystified. Anyone know how this works?

Oh, and this post is in response to a reader who thought we were gettting way too serious lately with all the negative news. So fine. I want to know how this works :-)