http://www.artnews.com/2013/02/21/chocolate-self-portraits-b...
Smelling the chocolate, and indeed the possibility of a transgressive viewer licking it, is definitely part of the piece. Brown paint wouldn't cut it.
On the subject of smelly rooms, I was able to experience the chocolate room by Anya Gallacio (http://beautifuldecay.com/2014/05/27/anya-gallaccio-creates-...), and let me say, a whole gallery room that smelled of chocolate was highly memorable. I did not lick the wall, but it was allowed. Delightful!