Hamburger, of course! This was kind of a rushed job, so I'm not 100% happy with it, but it definitely got the job done. The 'buns' are made from a simple whiskey yellow cake recipe, and the inside is a brownie. The frosting is a simple buttercream. I dyed all the frosting using a handy box of Wilton's Gel Food Coloring. The red and green didn't get as bright as I would have liked them, even with the gel coloring.
I'm still getting the hang of gel food coloring as opposed to the bottled kind...I used up more than my fair share of toothpicks in the process!