Add water and sugar to a saucepan over medium-high heat. Stir to dissolve the sugar completely and turn off the stove once the mixture starts to boil and looks clear.
Pour the sugar syrup into a clean bowl and let it cool down slightly. Gradually add the cooked glutinous rice flour in batches. Stir to combine thoroughly before adding a new batch.
After you have added about 2/3 of the flour, you will have a clumpy, sticky dough. Cover and let it rest for 10 minutes. Sprinkle a third of the remaining flour on a clean surface and place the dough on top of the flour. Sprinkle another third of flour on top of the dough.
Make sure your hands are clean, or put on food-grade gloves. Press down on the dough, then fold in half top-to-bottom and then left-to-right. Press down again and repeat. The dough will gradually absorb the dusting flour, becoming heavier and smoother.
Once the dough looks smooth, feels heavy and dense (but not hard), press down to flatten it and roll into a log. Cover and let it rest for 10 minutes. Divide the dough into 8 equal portions, about 1.4 oz (35-40gr) each. Lightly dust each dough piece and roll into a ball.
Divide the filling and shape into small balls. Flatten a dough ball and place the filling in the center and then seal. Dust your mooncake mold thoroughly and place the cake inside the mold. Press to shape the cake. Continue with the remaining dough and filling.
The cakes can be eaten after a few hours, but they will taste better the next day. Store in an airtight container at room temperature, and eat it within 3-4 days for the best taste and texture.