I ran out of time and couldn't make my own ice cream to sandwich inside the brownies, so I used store-bought coffee and vanilla. I was planning on rolling the vanilla ones in sprinkles for some color, and Jennifer suggested nuts for the coffee ones. However, the logistics of handling the super thin sheets of brownies and the melty ice cream totally screwed me! Hence the FAIL.
BUT: they were received more than warmly by the dinner party guests, and they did taste good despite their messiness and general unattractiveness. Hence the (mostly).
I shall try again and attempt to devise a way to make them without having the ice cream squirt out everywhere.