Mix Together The Warm Water, 1/2 Tsp. Sugar And Yeast In An 8 Oz. Measuring Cup. Let Stand Until It Rises To The 8 Oz. Level (About 20 Minutes). Sift Flour, Cake Flour, Sugar And Salt Into A Large Mixing Bowl. Add Shortening, Yeast Mixture And Milk. Knead Mixture 5 Minutes To Form A Dough. Cover With A Damp Cloth And Set Dough In A Warm Place. Allow The Dough To Rise For 3 Hours. Heat Wok, Add Oil And Stir-Fry Pork For 2 Minutes. Add 2 Tablespoons Water, Salt, Sugar, Soy Sauce, Oyster Sauce And Hoisin Sauce. Bring It To A Boil. Prepare Thickening By Mixing The Cornstarch And 4 Tablespoons Cold Water. Stir Into The Mixture And Cook For 1 Minute. Let Cool Before Using. After 3 Hours, When The Dough Has Risen, Shape Into Rolls About 2 Inches In Diameter. Cut Each Roll Into 1-1/2 Inch Pieces. Shape Each Piece Into A Shallow Bowl Shape. Put 1 Tablespoon Filling In The Center, Close And Twist Dough To Form A Bun. Put The Bun On A 2 Inch Square Of White Paper. (This Prevents The Bun From Becoming Soggy While Steaming.) Place 8 Buns In A Pie Pan And Allow Them To Set And Rist For 15 Minutes In A Warm Place.