In a medium-size mixing bowl, whisk together the golden syrup, oil, and kansui. Add the all-purpose flour to the bowl at once. Use a wooden spoon to mix everything together, until nearly all of the flour has been absorbed.

Use a silicone spatula (or any flexible spatula) to scrape the dry flour from the sides of the bowl and fold it into the dough. Keep scraping the sides of the bowl and folding the dough until it looks smooth and there is no dry flour left. The dough will feel slightly tacky to touch, but should not be overly sticky to touch. Cover the bowl with a damp towel or silicone lid and let the dough rest for 45 minutes to 1 hour.

Preheat the oven to 350ºF (175ºC). Line 2 large baking sheets with parchment paper and set aside.

Remove the top sheet of plastic (or parchment paper). Hold onto a piece of red bean paste with your left hand and drape the rolled out mooncake skin over the filling. Remove the other sheet of plastic or parchment paper.

Flip everything over so that the skin sits on the crook of your right hand. Wrap the skin around the filling and seal it up. If the skin rips during this stage, simply pinch the dough together. Once you finish wrapping the bean paste, roll everything in your hands until you get a smooth ball. (NOTE: I like rolling up the mooncakes this way because it doesn’t leave too many air pockets and it better ensures that the dough is evenly distributed throughout the cake. If there’s a more intuitive way for you to wrap the mooncakes, feel free to use it.)

Lightly dust your work surface. Roll the wrapped mooncake in the flour to lightly dust it. Then, gently roll the ball into a short oblong log. This will make the mooncake easier to slide into the mold.

Insert the mooncake into the mold and gently press it down with your thumbs. This helps to prevent the mooncake from falling out when you flip the mold over.

Flip the mooncake mold over a lightly floured surface. Use medium pressure to press down on the handle of the mooncake mold. Do not press down too hard or else the mooncake skin will start to squirt out from the bottom. Transfer the shaped mooncake to the parchment-lined baking sheet. Continue shaping 7 more mooncakes so that you have 8 mooncakes total.

Transfer the baking sheet to the oven and bake the mooncakes for 10 minutes.

While the first batch of mooncakes are baking, prepare the egg wash by whisking the egg and water together. I like to fully bake the first batch of mooncakes before moving on to the second batch. If your kitchen is hot, refrigerate the remaining mooncake skin and bean paste.

After 10 minutes of baking, remove the mooncakes from the oven. They should start to turn golden at the top.

I like to use 2 natural bristle brushes to apply egg wash. Dip the first brush into the egg wash and apply a very thin layer over a mooncake. Then, use the second brush to brush over the mooncake to remove excess egg wash. You don’t want to flood the indentations on the mooncake with egg wash because the design won’t come out as clearly. Continue applying egg wash to the remaining mooncakes. If you don’t have 2 brushes, just try your best to apply a thin layer of egg wash. You do not need to brush the sides of the mooncake with egg wash.

Freshly baked mooncakes are solid as a rock. They also tend to have some cracks at the top and the designs don’t look as sharp. This is completely normal. In general, you should wait 2 days before eating the mooncakes (even better if you are patient enough to wait for 3 days). During these 2 days, the moisture returns to the skin and softens it. The cracks on the mooncakes also fade away and you can see a shiny gloss develop at the top of the mooncakes. Of course, you can eat the mooncakes the day they’re made or the next day but expect dry mooncakes.

Store the mooncakes in an airtight container for up to 4 days. You can also store the mooncakes in the fridge for up to 8 or 9 days or freeze them for several months. Let the mooncakes reach room temperature before eating again.