Wash and cut up greens. In a large pot, bring 3 c water to a boil. If you wish, add ham hocks or pig tails for seasoning. Cook greens for about 45 minutes. Add an additional 3 c water. Bring to a boil for 10 minutes. Make dumplings by combining cornmeal, flour, baking powder and salt in a medium bowl. Slowly pour in warm milk (warm water can be added if milk is not available) Stir between additions. Dough should be slightly moist but not soupy. Scoop up mixture in large spoon. Shape into a small biscuit with finger tips. Drop dumplings on top of the greens and reduce heat to simmer. Cover and steam for 30 minutes or until dumplings are done. Use a dome lid to encourage steam.