For the dough,
Combine yeast and half the water. 1t sugar and 1t ap flour.
Mix well, cover with a warm towel and let rest in a warm place for 15 minutes.
Sift remaining flours adding remaining yeast, sugar, water and butter.
Using a wooden spoon, form a dough, knead for 5 minutes until smooth on a floured surface.
Place in a large oiled bowl, letting stand in a warm place, covered for an hour.
Punch down the dough, knead again for 5 minutes, divide into 16 pieces and roll out into 3 inch circles.
Cover dough with a damp towel, and ones at a time spoon 2t of filling into the center of each dough piece.
Gather edges together, twist off to close and cover with a damp towel.
Place all buns sealed side down on an individual parchment square and steam for 15 minutes.
Snip tops of buns twice in the same place at 180 degree angles to make a star and serve.

For the filling,
Heat oil in a large pan over high heat, adding the ginger and garlic.
Saute briefly and add the hoisin, sesame oil, soy and oyster sauce.
Cook briefly and add the cornstarch mix.
Heat briefly and add the pork and scallions, pull from heat and stir.
Allow to cool and utilize as needed.