SAUTÉ. Heat oil. Add onion and garlic until lightly brown. Add pork stirring regularly until lightly browned.
ADD THE REST OF INGREDIENTS. In a jar or bowl put water, soy sauce, oyster sauce, dark soy sauce, sugar, and star anise. Stir until well combined then add to the sautéed pork. Bring to boil.
COOK. Leave it simmering until the meat is tender.
STRAIN. Remove the meat with a slotted spoon and let it cool. Shred the meat using your hands or with two forks. Add 1/2 cup of the braising liquid used earlier to the meat then back to heat, bring to a boil.
In a bowl, combine cornstarch and about 1/4 cup water then stir until well dissolved. Add to the pot of meat and cook for 2 minutes whilst stirring and well thickened.
Use the braising liquid left from earlier. Add a tablespoon of cornstarch then bring to boil while stirring regularly until thickened.
HEAT MILK. Put milk and water in a bowl. Microwave for 1 minute until warm to touch.
MELT THE BUTTER. Put butter in a bowl, microwave for 30 seconds until melted.
MIX DRY INGREDIENTS. Add bread flour, sugar, salt, and yeast in a mixing bowl.
Add the melted butter and beaten eggs to the dry ingredients. Mix using a mixer until form like breadcrumbs. Add warm milk gradually while mixing. Knead the dough for 15-20 minutes until it pulls out from the sides of the mixing bowl.
Form the dough into a ball and place it into a lightly greased bowl. Cover with a damp cloth and leave it in a warm place for an hour.
Divide the dough into 28 pieces. Shape each into a small circle then roll flat using a rolling pin. (Not too thin!) Put a tablespoon of filling in each dough. Crimp them closed making sure that they are tightly sealed. Put each on the tray with seam side down on baking sheets.
Preheat oven to 200C.
Brush each rolled dough with eggwash and sprinkle with sesame seeds on top, if using. Leave it in a warm place for 30 minutes to an hour.
BAKE. Put a tray in the oven then turn the temperature down to 175C. Bake for 20-25 minutes until golden brown.
COOL DOWN. When cooked, place it to a cooling rack to prevent the bottom from being soggy.