back when I was living in SF, word went around the sort of parties I went to that someone's chemist friend made a vacuum-extracted cold-brew coffee concentrate he called The Black Blood of the Earth with some ridiculous concentration of caffeine.
I found out recently through one of the founder's tweets that the BBotE enterprise was now large enough that you can just order it online so I decided to follow up on my curiosity from like a decade ago.
flavor: the official tasting notes describe it as "black pepper and cakey brownies". I'd say up front it tastes kind of like metal and grit but with a pleasant, lingering dark chocolate aftertaste.
caffeine: twice I've had about 2 fluid ounces of this stuff and somehow, despite not making me feel perceptibly more alert, it has taken me directly into the vaguely sweaty and nauseated feeling of low-level caffeine overdose.
when my mom was over this weekend helping me with a project, not only did she complain that the first 2 ounces didn't do anything, but she went back for seconds. I fear her.