Start at 0.5%
There is nothing like the taste of Cocoa! FlavourArt has perfected the taste of the delicious South American Cocoa Bean! Try it yourself!
FA Cocoa and TFA white chocolate makes an AMAZING dark chocolate flavour. The white chocolate really just carries the flavour and you don't have the syrupy notes from a milk chocolate concentrate getting in the way.
1% reads distinctly like darker cocoa. Tastes a bit roasted without having any kind of burnt notes. 1.5% has an even darker chocolate, and you can start to really pick out that marshamllow-y note to the sweetness here. By 2% it's getting a bit bitter and honestly a bit much. I'd start low and work up with this