Dissolve yeast in warm water in a large mixing bowl. Stir in molasses, caraway seeds, salt, shortening, rye flour, quarter 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 190ºC or 25 to 30 minutes or until loaves sound hollow when tapped. Remove from baking sheet, and let cool on wire racks. ----