Combine the flours in a large bowl. Reserve 3 cups of the flour mixture. Sprinkle yeast over the warm water and stir until dissolved. Mix together the reserved 3 cups of flour, cocoa, sugar, caraway seeds, salt and instant coffee.
Combine the water, vinegar, corn syrup and butter in a medium saucepan. Heat over low heat until just warm, butter does not need to be completely melted. Add to the cocoa mixture and blend well. Add the dissolved yeast and stir until thoroughly combined. Stir in enough additional flour mixture, one cup at a time, until the dough no longer clings to the sides of the bowl.
Turn the dough onto a lightly floured board. Cover and let rise for 10 minutes. Knead the dough until smooth and elastic, about 15 minutes (see video below for instructions on kneading). Place in a greased bowl and turn the greased side up. Cover and let rise in a warm place about 1 hour or until double.
Punch down and turn onto a lightly floured board. Divide the dough in half and shape each portion into a smooth ball. Place each ball in the center of a greased 8 inch round cake pan. Cover and let rise in a warm place about 1 hour or until double.
Bake at 350°F for 45-50 minutes or until the loaves sound hollow when tapped lightly. Remove from the pans and place on wire racks.