I need to stick some fondant (rolled buttercream) shapes onto a buttercream-iced cake. Can anyone tell me what type of icing to use to stick the shapes onto the cake?

The buttercream icing on the cake is a crusting recipe, so I'm worried if I just use that icing on the backs of the fondant shapes, they're going to fall off when it hardens.

Any suggestions? Would a bit of corn syrup on the back of the shapes hold?

Thanks!

I usually just brush the back of my fondant decorations with a little water. Works like a charm.

If the fondant accents aren't too heavy, I just stick 'em right on the buttercream without any "glue" at all. Never had a problem.