here's a good thread on it: http://www.homebrewtalk.com/f37/chocolate-stout-question-50985-post518774/
I devised up an AG recipe the other day, but a basic extract version of it would be:
6.6lbs dark dme
maybe steep a pound of chocolate malt maybe a half pound of caraffa III
I went with hallertau hops to about 28ibu's
a pound of lactose
8oz bakers chocolate in the end of the boil
8 oz semi-sweet chocolate at secondary.
That's real basic because I don't have the file on hand, but you get the basics of it.