I currently have a batch of Irish stout in secondary (Kit from Midwest Homebrewing with added grains), and will likely be bottling in a few days, and I have been mulling over the idea of a caffine enhanced brew. I've heard about brewing coffe with the boil, as well as adding brewed coffee to the batch at bottling, and was wondering if anyone has tried using a few shots of espresso to add that extra zip. Two concerns I have are that the oils from the espresso would negatively impact head retention, and that it might introduce unwanted bitterness. I would think that since the coffee wasn't being boiled with the wart, there would be less of that nasty oil slick effect (we all have tried to drink a cup of coffe after it has been sitting and boiling in the pot all day, ugh!), and espresso could add a noticable flavor (and jolt ) without needing to add a large quantity of non-beer liquid, but I can only guess about all that. Any ideas, thoughts?