This would be tied to your glitch's in-game "birthday," and could operate similarly to Zilloween or Pi Day.
Basically, every individual player would only get to know the recipe for Birthday Cake for only a few days every year, but *someone* would always know it. During your birthday, you could mass-produce as many whole cakes as you wanted. Then, you could either sell them whole in the auction house, or slice them up and give the slices away. I think it would make some really interesting dynamics if there was a rare-ish item that everyone eventually got a chance to control the market.
I'd also like it if this was clearly an item meant to be shared. Instead of earning a badge for eating a certain amount by yourself, there could be rewards for giving away slices, and for eating slices of other peoples' cakes.