This way my first attempt at a challah (Peter Reinhart's Crust and Crumb) and I have to say that the crumb is just amazing. Unfortunately, the egg yolk wash didn't go as planned. I have washed plenty of breads before, but I have never had this type of blackening happen to me before. Dark brown, sure, but this was nuts. I have two hunches; 1) I used coconut sugar instead of regular white sugar, and 2) I used a little bit of olive oil when kneading to keep things moist so as not to dry out the dough with too much flour.
Any thoughts on why this might have happened to me?