Add 1 cup bread flour, cocoa powder, sugar, salt, onion powder, and yeast to stand mixer bowl; whisk to combine. Add coffee, oil and molasses to flour mixture. Mix with paddle attachment for 4 minutes on medium speed.

Switch to dough hook attachment. Gradually add rye flour and enough of the remaining bread flour to form a firm dough. Knead until smooth and elastic, about 5 to 7 minutes.(NOTE: For hand mixing: following above steps, mix ingredients in large mixing bowl using a wooden spoon or dough whisk. Knead on floured surface until smooth and elastic.)

Place dough in lightly oiled bowl and turn to grease top. Cover; let rise until indentation remains after poking dough with finger down to second knuckle, about an hour.

Turn dough onto lightly floured surface; punch down to remove air bubbles. On lightly floured surface, shape dough into a round loaf. Place on lightly greased cookie sheet or in 8-inch layer cake pan. Cover; let rise in warm place until indentation remains after touching (about 30 minutes).

Preheat oven to 400°F.

Bake for 30 to 35 minutes. Remove from pan; cool before slicing.(Optional: Combine ¼ cup water and ½ teaspoon cornstarch; heat to boiling. Five minutes before the loaf is finished baking, remove from oven and brush top with cornstarch glaze. Sprinkle with caraway seeds, if desired. Return to oven and bake approximately five more minutes until glaze is glossy and loaf sounds hollow when tapped.)