Preheat the oven to 180°C/356°F (without fan).
Bake the mooncakes for 10 minutes.
Remove the baking tray from the oven and let the cakes cool for 10 minutes.
Reduce the oven temperature to 160°F/320°F (without fan).
Meanwhile, make the Egg Wash by whisking the egg with some water in a small bowl.
Lightly brush the mooncakes with the Egg Wash, using a pastry brush with fine bristles (a silicon brush picks up too much egg wash for this task). Try to avoid putting too much Egg Wash onto the intricate patterns on the surface. If you have too much Egg Wash on the cakes, use some kitchen paper to blot the cakes.
Return the baking tray to the oven.
Continue baking the mooncakes for 10-15 minutes, or until they are golden brown all over.
Let the mooncakes cool completely on the baking tray, which will allow them to develop a crisp bottom.