Made this Chocolate Chocolate Challah (an eGullet recipe) today; unsweetened cocoa powder in the dough and dark chocolate chunks kneaded in. Smells delumptious...cooling down now. I know there are Sourdough [u]Plain[/u] Challahs, but can a chocolate one be made from natural leaven? Someone said he tried but it didn't work...just won't budge. What impedes the proving of the dough?