Heat the oil in a wok. Sauté the ginger, onion and shallots until fragrant. Add chicken stock powder, oyster sauce, dark and light soy sauce, and sesame oil. Mix well and add the pork and water. Simmer until almost dry.
To thicken the gravy, mix the Hong Kong flour and water chestnut powder with a little water and add to the wok. Add spring onions and season to taste with sugar and salt. Set aside.
To make pastry:
Knead pastry ingredients in a mixing bowl to a smooth elastic dough. Cover and rest for 10 minutes. Shape into balls (40g each).
To make topping:
In a bowl, mix the margarine, icing sugar and salt. Slowly mix in the egg. Fold in the flour, milk powder and baking powder.
Fill the dough balls with the cooled filling, reshape and leave to rise slightly before piping on the topping cream. Side aside to proof.
Bake in a preheated oven at 200 degree Celcius for 10 to 12 minutes.