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 and 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!