01 - Preheat oven to 350°F. Line a baking sheet with parchment paper.
02 - Whisk together golden syrup, vegetable oil, and alkaline water in a mixing bowl until thoroughly combined and smooth.
03 - Add flour to the liquid mixture and stir until a soft dough forms. Cover and let rest at room temperature for 30 minutes.
04 - Divide lotus seed paste into 12 equal portions (approximately 40 g or 1.4 oz each). If using salted egg yolks, encase one yolk in the center of each paste portion and roll into smooth balls.
05 - Divide the rested dough into 12 equal pieces (approximately 25 g or 0.9 oz each).
06 - Flatten one dough portion into a thin disc. Place a filling ball in the center and carefully wrap the dough around it, sealing completely to enclose the filling. Repeat with remaining portions.
07 - Lightly dust each ball with flour. Press firmly into a floured mooncake mold to imprint the design, then invert to release onto the prepared baking sheet.
08 - Bake for 5 minutes, then remove from oven and allow to cool for 10 minutes.
09 - Whisk egg yolk with water. Brush a thin, even layer over the surface of each partially baked mooncake.
10 - Return to the oven and bake for an additional 15 to 20 minutes, or until the tops develop a rich golden-brown color.
11 - Allow mooncakes to cool completely on the baking sheet. Transfer to an airtight container and store for 1 to 2 days before serving—this resting period allows the pastry skin to soften and develop the traditional texture.