My girlfriend and I have been to some restaurants that offer Young's Double Chocolate Stout with a shot or so of Lindeman's Framboise in it to give it even more of a "dessert beer" flavor. It's something you wouldn't want after mowing the lawn, but I have to admit that it does taste good with a cake.
So I researched different recipes for a while to see what the best balance would be. Seeing that most people didn't want an overwhelming raspberry or chocolate flavor, I then threw all of the research on the adjuncts out the window.
I found a deal on bulk raspberries -- I can't imagine how expensive they'd be buying from the grocery store. I pureed five pounds... FIVE POUNDS... of raspberries. I put the puree on the stove and added 10 oz of Ghirardelli Unsweetened Cocoa, and stirred it up until it reached 180 degrees. I removed it from the heat, let it sit with the cover on for 30 minutes or so until it had cooled off a bit. Stirred it around to cool it some more.
I added this to directly to the primary on top of the fermented milk stout using a sanitized funnel and scooper -- worried a little bit about oxidation since it was dropping into the beer. This way, however, the yeast would get to work right away on the raspberry sugars and I would only have to transfer for clearing once, hopefully. Fermentation has since started up again -- bubbling quite a bit -- and the krausen is a dark chocolate color.
This beer is either going to be vile... or incredible. We'll see.