In a bowl, mix together the warm water, 1 Tbsp of sugar and yeast. Let stand for 5 minutes.
In a big bowl, combine the flour, rest of sugar and baking powder. Add the liquid to the dry ingredients and the 3 Tbsp shortening. Mix well until a dough forms.
Turn dough out onto a lightly floured surface. Knead the dough for 5 minutes or until smooth and elastic. Coat the dough with oil and place in a bowl. Cover the bowl with plastic wrap and let the dough rise for an hour or until it doubled in size.
Punch the dough down and turn it out onto a floured surface. Roll into a log and divide into 8-10 equal portions.
Form one into a ball and then using hand of rolling pin flatten it into about 4-5 inch circle leaving a small bulge in the middle. Scoop a tablespoon of filling and place it in the middle. Gather the ends towards the middle from one side until you reach the other end closing the filling in. Pinch and twist to seal the ends together o top. Repeat with the remaining dough balls. Let them rest for 5-10 minutes.
Before steaming, put a piece of parchment or wax paper at the bottom of each bun. Place the buns in the steamer leaving at least an each apart as they will rise and spread while steaming. Steam for 15 minutes. Turn off the steamer or remove from heat and let it stay closed for 5 minutes before removing the cover.
Let the buns cool a bit before serving.
You may also use instant yeast and add it directly to the flour or dough without the need of proofing it first.