My favorite chocolate in all the world (at the moment, and has been for a couple years) is Patric Chocolate. The bars are available at my favorite chocolate store, The Meadow, in Portland, but also online. Once a month, the online store opens for a couple days, and you can buy the most amazing chocolate in the world.
The bars come sealed in a plastic wrap, and wrapped in a thick paper / thin cardboard folded envelope. I really like the paper the envelope is made of, so I've been cutting off the envelope tabs, and keeping the main part of the envelope. I have a stack a couple centimeters thick of these cards. I've sent some as postcards, I like them so much.
Recently, I've wondered how they would do as a water color surface.
Answer: surprisingly well. It isn't as good as good watercolor paper, which is fine, but is better than copier paper (oh, I crack me up).
After this experiment, I painted a few hearts on the front of another card, addressed it to my brother, and mailed it off. Won't he be surprised at the heart-cow-chocolate postcard!
Though, now that I think about it, it's from me. He won't be surprised.