In a bowl, mix golden syrup, vegetable oil, and alkaline water until well combined.
Gradually add flour and mix to form a smooth dough. Let it rest for about 30 minutes.
Divide the filling into small balls and place a salted egg yolk in the center if desired.
Flatten the dough pieces and wrap them around the filling balls.
Place the shaped mooncakes into a mooncake mold and press to create patterns.
Arrange them on a baking tray and lightly brush the tops with egg wash.
Bake in a preheated oven at 180°C (350°F) for about 15–20 minutes until golden brown. Allow to cool before serving.