Won't work in a straight mead, but I have a braggot (malted mead) going that I used 1 oz of cocao nibs each at the mash, 1/2 hour boil, and 10 min of boil. You can definately taste the bitter chocolate from it.
However you use them (my point was that you can add the cacao nibs at any point, and get different flavours from each, I'm sure), I would say maybe 3-4 oz per gallon, and if they are unroasted, you should do so by lightly cooking them in a dry frying pan (or baking).
You don't need to boil the honey either, it's fine as is unless you want caramelly flavours in your mead (making it a bochet).
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