How or when did it fall apart??
This cake has a 12" chocolate cake on the bottom. Recipes are on the second link.
It came apart when I tried to fill it and put the layers together (it cooled overnight, so I know that wasn't it)! I've used this recipe as a normal sized (9 in) two-layer cake and never had this problem. To be honest, it seemed extra dry!
When you were filling it and trying to put the layers together did you use something to 'support' the layers while you moved them, or did you just pick them up with your hands?