>>these compounds are extremely delicate, and are often destroyed during conventional cocoa processing processes

If you mean the roasting process that converts cacao into 'Dutch process' cocoa, then yeah. Roasting also produces acrylamide (same as roasting coffee) which is a carcinogen.

So cacao powder (not cocoa). But... you have to pay attention to where it's from. The tree cacao pods are harvested from will take up cadmium from the soil if any is present. Cadmium is high in Denmark, The Netherlands (probably from past soil amendments), and Latin America (naturally higher levels there). I lean towards cacao from West Africa for this reason.

We humans are not at all good at excreting cadmium so it sticks around - and is a known carcinogen.

If you're now worrying about your chocolate bar - don't. There's hardly any in cocoa in there, excepting the 70% (and up) dark. Basically, if nobody ever says "how can you eat this?" you're fine.