I can see how the selection of gin, genever, and vermouth will all have a profound impact on the flavor profile. My first try, following the recipe as given, was good but not great (3.5). For my second try, I bumped up the cacao (1.5 oz) and bitters (10 drops) to try and make the chocolate flavor stand out over the base spirits and vermouth. It was a little better, but I wonder how many people, blindfolded, would identify this as a chocolate-flavored drink?
Not sure how you are not feeling the chocolate. It is easily the predominant flavour even with the recipe stated above. I tried also with vanilla vodka, creme de cacoa white and, noily prat with 4 dashes of chocolate bitters and it worked a treat