I have brewed a couple chocolate beers. Best NOT to use chocolate, but rather baker's cocoa.
I did a test with a 10 gallon batch. During sparge I added a quarter pound of organic baker's cocoa. I split the btach into two five gallon batches and added an extra eigth pound to one fermenter (doubling the cocoa content in that batch). I did a blind taste test with qualified judges and the jury was split evenly. Half preferred the extra cocoa version and half preferred the lower cocoa version. And it was actually evenly split by gender as well - the jury was two women and two men and the genders split evenly on their preference, in other words, gender made no difference.
Have fun with this. I liked the results of my batches quite a lot!
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