Well, maybe not a cake--more like a hot pink puffed rice cookie...Anyway, here's a nice way to make a mould for any pourable confection that doesn't require baking.
Step 1: Draw your footprint.
If you have a computer file, print it out. If you want to draw freehand, do it. I wanted to use the MAKE Magazine logo to celebrate our first birthday, and decided to try drawing it freehand.
I used a waxed paper box as the basis for my line width. I had the logo on a magazine cover as reference, and used a ruler to help me judge the width and height of each letter in reference to each other letter. It's not a perfect rendition, but it's pretty close.