I used to attribute the dark color of pumpernickel to its rye flour, but it is in fact artificial, typically contributed by added cocoa powder or caramel color. Even knowing this secret, the rich dark color combined with the slight bitterness of rye adds a certain air of sophistication. Why not bagelize this idea? Or pumpernickelize the bagel? Here’s my approach: replace 20% of the flour with rye flour and 3% with cocoa powder. Double the sugar to counteract the bitterness of the cocoa powder and rye.