This trick is totally impromptu magic trick only one coin is used here it's http://www.youtube.com/watch?list=UUv0oyOTdsiZqTsOwweite1w&v=M9CpYnj1e9I&feature=player_detailpage
The cake took me 5 hours to build and I used over 165 cards from 6 decks but it worth it here is the view from the front
http://imgur.com/Y0qGT
and here is the view from the top http://imgur.com/oQl7H