In a large bowl combine the yeast, warm water, and sugar and stir. Let the yeast sit for 10 minutes or until the top is foamy.
Add to the yeast mixture, flour, baking powder and cut in shortening. mix well until a dough forms. Knead the dough for ten minutes until smooth and elastic. more flour may be needed if it's too sticky.
Place the dough in a large, oiled bowl and cover it. Put it in a warm place for 1-2 hrs. until it has tripled in size.
Knead the dough again until smooth and elastic.
Separate the dough into 4 sections. then roll those sections into logs and cut 4 more sections each. You should now have 16 balls of dough.
Flatten the dough into circles. pat the dough down and then pinch and flatten the edges thinner than the center.
Add 1-1 1/2 tablespoons of filling in the center.
Fold the circle in half and pinch the very center. Rotate and fold in half the other direction pinching in the center. You should now have an x shaped top. bring the points of the x together pinching hard so that it really sticks. (This is hard to explain in text format see video above for a better explanation)
Wait 10 minutes for the baos to rise again before steaming.
Line the steamer with parchment or steamer liners. Place the baos 2 inches apart from each other.
Add 1 1/2 -2 inches water to a pan. Place steamer on top and bring to a boil.
Steam for 12 minutes. Remove the baos carefully as the steam will burn you.
Repeat until all the baos are cooked. Check the water level after every round to make sure you have enough in the pan. Baos can be wrapped tightly and frozen for up to 3 months. To reheat just steam for 5 minutes.