Want to make the astronomy-loving person in your life very happy? Bake this spherical cake modeled after Jupiter, complete with layered insides representing the planet's rock and ice core, layer of liquid metallic hydrogen and outer layer composed of molecular hydrogen. So cool!
The concentric layers are made from the inside out. First you bake the tiny core layer, embed it into the batter for the next layer, bake and proceed. It's definitely not a baking project for the faint of heart, but it might be the greatest cake you could ever make for your favorite geek.
Cakecrumbs has a video tutorial which lays out the process step by step.
What's the most ambitious cake you've ever made?