sundae/cake milkshake?

[girl_in_blue]

somewhat inpired by the previous artery-clogging post, i have a question about those american frappuccino/milkshake things that have cake in them (when i lived in the us, starbucks had one that had a brownie blended into it - so wrong, but so delicious). it was my boyfriend's birthday a few days ago and i made him a cake. it was delicious but we only got through half of it and now the other half is a bit stale. i was thinking a good way not to waste it might be to blend it up with ice-cream/soy milk. has anyone ever done this? any recipes/proportion/ingredient suggestions for me? the cake was espresso flavoured.

thanks!