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 ounces each). If using salted egg yolks, place one yolk in the center of each paste portion and shape into a smooth ball.
05 - Divide the rested dough into 12 equal pieces (approximately 0.9 ounces each).
06 - Flatten a dough piece into a thin disc. Place a filling ball in the center and carefully wrap the dough around it, sealing completely. Repeat for all portions.
07 - Lightly dust each ball with flour. Place into a floured mooncake mold and press firmly to imprint the design. Invert the mold to release the shaped mooncake onto the baking tray.
08 - Bake for 5 minutes, then remove from oven and let cool for 10 minutes.
09 - Whisk egg yolk and water together until blended. Brush a thin, even layer over the cooled mooncakes.
10 - Return mooncakes to the oven and bake for an additional 15 to 20 minutes, or until golden brown.
11 - Cool completely on the baking tray. Store in an airtight container for 1 to 2 days to allow the skin to soften and develop traditional texture before serving.