It wasn't yet sold as anything but a beverage, that wouldn't happen until 1828 or thereabouts, but the nobility had access to it in all forms as far as I know. When MT recommends chocolate to all her friends as ideal to lift the spirits and help with concentration, she's mostly thinking of the beverage, but Viennese cooks also used to pour it over some other pastry and use it as a cover. No idea whether Fritz knew it as anything but a beverage, I was just improvising. ;)