Smash the unpeeled ginger with the flat of a heavy cleaver so that it will release its juices. Put the ginger in the cup of water, stir, and set aside. 1 to 2 hours is preferable. Add the sugar and the yeast to the cup of lukewarm water and stir until it dissolves. In the meantime, sift the flour into a bowl. When the yeast mixture is foaming, add it to the flour and mix vigorously until the mass begins to stick together. Add the oil and when the dough coheres enough, place it on a floured counter and knead for 10 minutes until it is smooth. It is very important that the dough be soft. Do not add more flour unless necessary to keep it from sticking to your hands and the kneading surface. Once the dough is kneaded, oil the dough ball with peanut oil and place in a covered bowl in a warm place. Separate and blanch the cabbage leaves for 3 minutes in a large pot of boiling water. Remove, drain, and cool. When it is cool enough to handle, roughly chop the cabbage and put in a clean hand towel. Wring out as much of the water as possible, then mince. Mix together the pork, cabbage, the minced ginger, minced scallion, minced garlic, salt and pepper. Mixing thoroughly with a wooden spoon or paddle of a kitchen mixer, add the cup of strained ginger water, soy, wine and sesame oil. Add cornstarch, and mix in one direction for several minutes. The filling should be moist, almost like batter; add chicken stock if the filling seems stiff or dry. Have the steamer ready before you begin. When the dough has doubled in bulk, and you are ready to make the baozi, punch down the dough and make several indentations in the dough with your fingers. Sift the baking powder into these holes, fold up the dough and pinch the edges together to contain the baking powder. Knead for five minutes, or until the baking powder is thoroughly incorporated. Cover the dough ball and let it rest for five or ten minutes. Form the dough into two ropes, approximately 1-1/2" in diameter, then cut the ropes into sections approximately 1-1/2" long. Roll each segment into a ball, place, separated, on a tray, and cover. To make a baozi, flatten one of the balls with your hand, keeping it as round as possible. Roll the discs into approximately 4" rounds, as thin as possible on the edges, and 1/8" or so in the center. Roll out several rounds and keep them covered as you begin to fill the baozi (Doing these somewhat ahead once again rests the dough and makes them more manageable). Smear a couple of heaping tablespoons of filling to the dough, leaving a border of a half inch or so, and begin pleating the very edge with your fingers and thumb, overlapping the dough by a quarter inch or so. The pleat should be squeezed firmly and pulled slightly vertically to prevent the top of the finished bun from being too thick. As you pleat, rotate the baozi clockwise, making sure the filling remains well below the edges of the bun. Complete the process by closing the top with a spiral twist. Place the pleated baozi, separated from one another, on a steamer tray lined with perforated parchment paper or (napa) cabbage leaves and steam, covered, for 14 to 15 minutes. It is very important to make one or two sample baozi to test for salt and seasonings. When you've done this, you are ready to complete the batch of 20 - 30 baozi.