The chocolate taste is generally pretty subtle in these beers, despite the name. It usually comes from the use of "chocolate malt," which is just darkly roasted barley. So the predominant flavors/smells are generic roasted notes with subtle hints of cocoa, chocolate and coffee - to varying degrees depending on the beer. Its not like drinking a chocolate milkshake or anything like that. If you've ever tried a Guinness then you might be more familiar with the taste then you realize. Imagine a Guinness with just a little bit of extra (but still very subtle) chocolate notes. Apologies if this comes across as me "man-splaining" or patronizing (not my intention).
You should totally take part in #Beersaturday!!
RE: Chocolate Stout and a Porter