Dissolve yeast in warm water in a large mixing bowl. Stir in molasses, caraway seeds, salt, shortening, rye flour, 1/4 cup cornmeal, and cocoa. Beat at medium speed of an electric mixer until smooth. Stir in enough all-purpose flour to make a stiff dough. Turn dough out onto a lightly floured surface. Cover and let rest 10 to 15 minutes. Knead until smooth and elastic (5 to 10 minutes). Shape dough into a ball, and place in a well-greased bowl, turning to grease top. Cover and let rise in a warm place (85 degrees), free from drafts, 1 hour or until doubled in bulk. Punch dough down; shape into a ball. Cover and let rise in a warm place, free from drafts, about 40 minutes or until doubled in bulk. Grease a baking sheet, and sprinkle with cornmeal. Punch dough down, and divide in half. Shape each half into a round, slightly flat loaf. Place loaves on opposite corners of baking sheet. Cover and let rise in a warm place, free from drafts, 1 hour. Bake at 375 degrees for 25 to 30 minutes or until loaves sound hollow when tapped. Remove from baking sheet, and let cool on wire racks. ----