In stand mixer bowl, add 2 cups bread flour, yeast, bran cereal, salt, caraway seed and onion powder; mix well. In saucepan, heat milk, water, molasses and chocolate to 120-130°F; stir until chocolate is melted. Add warm milk mixture to flour mixture. Using a paddle attachment, blend on low speed until moistened; beat on medium speed for 3 minutes.
Switch to dough hook attachment. Gradually stir in rye flour and enough remaining bread flour to make a soft dough. Knead until smooth and elastic, about 5 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 1 hour.
Punch down dough. Divide into 2 parts. On lightly floured surface, shape each half into a round loaf. Place in greased 8-inch round cake pans. Cover; let rise until indentation remains after lightly touching.
Preheat oven to 375°F.
Bake in preheated 375°F oven 40 to 45 minutes. (see glaze step below)
Make glaze: combine water and cornstarch; heat to boiling. Brush on loaves 5 minutes before end of baking. Sprinkle caraway seeds on loaves. Return to oven for 5 minutes or until glaze is glossy. Remove from pans; cool on rack.