Bread Baker's Apprentice Challenge is marbled rye bread.
To make the beautiful spiral, you start by making two doughs. Both doughs are made with rye flour, molasses and caraway seeds- among other ingredients- and the dark rye color is made by using cocoa and water.
I split each dough into four balls and rolled the balls out. I stacked light, dark, light dark and then rolled the dough into a loaf.