They've done other HP cakes for other movie premieres too. I remember seeing them do the Hogwarts Express and I think they mentioned having done another one.
I hate having to be the nerd to do this, but that's Hermione using Lumus Solem on the Devil's snare that was part of the protections on the Sorcerer's Stone. In the book she uses the spell that makes the fire she kept in jars.
I love Ornithology, Black, M