Originally Posted by Gordie
The thing to be worried about with head retention is the cacao butter and oils. the nibs are pretty low to negligible in the fats so boiling them probably wouldn't add much. Actually taking cacao and adding to the boil would be a substantial addition of fat.
Nibs are roasted, dehusked, lightly crushed beans. They still contain the full amount of cocoa butter that was originally in the bean (though you'll probably extract less than if you added chocolate liquor, which is nibs that have been finely ground to release the fat). To entirely avoid adding the fats you would have to use the the separated cocoa solids, which are sold as cocoa powder in your friendly neighbourhood grocer's.