Combine 1/2 cup all-purpose flour, yeast, sugar, and 3/4 cup water; let stand 5 minutes.
Add remaining water, rye flour, cocoa, salt, caraway seeds, molasses, and butter to yeast mixture; stir well. Add enough remaining all-purpose flour to make a soft dough. Turn dough out onto a floured surface; knead 10 minutes or until smooth and elastic. Place in a greased bowl, turning to grease top. Cover and let rise in a warm place (85°), free from drafts, 1 hour or until doubled in bulk.
Punch dough down; divide in half. Shape each half into a ball. Place each ball in a greased 8- inch round cake pan. Cover and repeat rising procedure 1 hour or until doubled in bulk.
Bake at 400° for 25 minutes or until loaves sound hollow when tapped. Remove from pans; cool on wire racks.