01 - Preheat oven to 350°F. Line a baking tray with parchment paper.
02 - In a bowl, combine golden syrup, vegetable oil, and alkaline water. Stir until smooth and well incorporated.
03 - Add flour to the wet ingredients and mix into a soft, pliable dough. Cover and let rest for 30 minutes at room temperature.
04 - Divide lotus seed paste into 12 equal portions (approximately 1.4 oz each). If using salted egg yolks, place one yolk in the center of each paste ball and enclose it, shaping into smooth spheres.
05 - Divide rested dough into 12 equal pieces (approximately 0.9 oz each).
06 - Flatten a dough piece into a thin disc. Place a filling ball in the center and wrap the dough completely around it, pinching edges to seal securely. Repeat for all portions.
07 - Lightly dust each ball with flour. Place into a floured mooncake mold and press firmly to imprint pattern. Invert mold and gently release onto the prepared baking tray.
08 - Bake for 5 minutes, then remove from oven and let cool for 10 minutes.
09 - Whisk egg yolk with water until combined. Brush a thin, even layer over the cooled mooncakes using a pastry brush.
10 - Return mooncakes to oven and bake for an additional 15 to 20 minutes, or until golden brown.
11 - Cool completely on the baking tray. Transfer to an airtight container and store for 1 to 2 days to allow the pastry skin to soften and develop proper texture before serving.