Preheat oven to 325°F/163°C.
Before baking, lightly spray the mooncakes with water.
Bake the mooncakes at 325°F/163°C for 10 minutes.
Remove the mooncakes and reduce the oven temperature to 300°F/149°C.
Let the mooncakes cool for 15 minutes.
In a small bowl, beat together egg yolk with 1 teaspoon water.
Lightly brush the mooncakes with egg wash (avoiding the indented areas to retain the imprinted design).
Wait 2 minutes for egg wash to dry and apply a second light coating of egg wash.
After 15 minutes, return the mooncakes back into the oven at 300°F/149°C for 12-15 minutes, until golden in colour.
Remove the mooncakes from the oven and let them cool on a wire rack.
Store cooled mooncakes in an airtight container, lined with parchment paper.
Let mooncakes sit for 2 days at room temperature before serving.