According to :
I think the reason Steve wants to use powders instead of whole spices
is that he's making his hot chocolate by pouring hot water in, rather
than by simmering. I'm not sure you can really extract much flavour
from a cinnamon stick just by sitting it in hot water. I could be
wrong though!

Ah, I see what you mean. I assumed he was worried about it 'going off'
rather than being ineffective.

To go back to the original post - to convert from the 'real' items to
the powdered version, it's probably only possible to do by trial and
error, as a lot of these things are a case of personal taste anyhow.

--