Can spherification be done with hot liquids?
You might be able to use konjac flour, but you'll need to raise the pH.  Start with Dutch process cocoa, as regular cocoa is acidic.

From Guy Crosby (the science guy on America's Test Kitchen): 


  But even more surprising, when the pH of a viscous 1% dispersion of konjac flour is raised to pH 9-10.5 by the addition of a mild alkali, then heated to about 85° C (185° F) for 20 minutes, and cooled, the sol transforms into a very firm, but elastic heat-stable gel. So stable that it will not melt even when placed in a 177° C (350° F) pan or oven!