I'd suggest perusing the Stout recipe database to see what other highly-rated stouts (sort by the rating column) contain. Off of the first page, I come up with this
, both of which meet your criteria (except they do indeed use actual coffee).
I'm not saying you should absolutely use one of those recipes (neither of which I've tried myself, I might add), but that they'll give you a good idea of what others are using in chocolate-coffee-oriented stouts. (For coffee-esque flavors without actual coffee beans, I would think a balance between chocolate and black patent malts, but I'll defer that information to someone more experienced with all-grain batches than myself.) Then incorporate a few ideas of your own and post the recipe you come up with for critique. You'll get more specific (and probably more helpful) feedback in this manner. Good luck!