Mix the cornstarch, all-purpose flour, and half of the sugar together in a small bowl.

Place the egg yolks in a large bowl. Stir a few times to mix the yolks.

Add the milk and the remaining half of the sugar into a small saucepan. Heat over medium heat. Stir occasionally to dissolve the sugar completely. Cook until it reaches about 120°F/ 49°C (no more than 150°F / 65°C). You might see a few bubbles here and there. If the milk starts foaming, it’s too hot.

While the milk starts to get warm, add the dry ingredients (from step 1) into the bowl with the egg yolks. Whisk until it forms an even paste. Do not add the dry ingredients too early, because the sugar will change the texture of the eggs.

Add the warm milk into the egg yolk mixture, about 1/4 cup at a time. Whisk constantly until the milk is fully incorporated into the paste. Continue to add more milk a 1/4 cup at a time and keep stirring, until it forms a thin, smooth mixture and all the milk is added.

Return the mixture back into the pot (the one you used to heat the milk). Heat over medium heat and stir constantly while scraping the bottom (to prevent from burning), until the mixture thickens. Keep cooking and stirring, until it starts to bubble. Stop your spatula for a moment to make sure that the custard is boiling. Keep stirring and boiling for one full minute. This is important so the custard will be able to thicken after chilling.

Remove the pot from the stove. Add the butter and vanilla extract. Stir to mix well.

Line a large deep plate with plastic wrap. Place a large mesh strainer on top.

Pour the custard into the lined plate over the strainer to smooth out the texture. Use a spatula to press the strainer if any lumps remain.

Cover the custard with plastic wrap. Press the wrap against the custard, so it won’t form a skin once it’s chilled.

Chill the custard in the fridge until it’s cooled completely, 2 hours or so. Or in the freezer for 30 mins.

Prepare a large bowl that can fit into your steamer. Place a large strainer on top.

In another medium-sized bowl, add the glutinous rice flour, rice flour, and cornstarch. Mix well with a fork.

Line a large mesh strainer over the bowl and sift the confectioner's sugar through it. Use your fingers or a spoon to press the sugar through if any lumps exist.

Add the milk, oil, and vanilla extract into a small bowl. Stir to mix well.

Use your fork to form a hole in the middle of the flour. Add 2 to 3 tablespoons of the milk mixture at a time. Stir until the liquid is incorporated into the flour completely. Repeat the process until it forms a very runny batter.

Pour the mixture into the large bowl (you prepared in step 1) over the strainer. Press the lumps using a spoon. Once strained, the mixture will thicken a little bit.

Prepare a steamer by pouring 1 inch (2.5 cm) of water into the steamer pot. Cover and heat over medium-high heat until boiling. Place the bowl with the batter into the steamer rack. Place the rack over the boiling pot. Cover and steam until the batter is cooked completely, 25 to 30 minutes. After 25 minutes, examine the dough by inserting a spoon into the middle. The spoon should come out clean, and the dough should feel very stiff.

Once done, remove the lid, and transfer the steaming rack with the bowl onto your kitchen counter to cool off for a few minutes.

Fold a kitchen towel a few times and place it on your working surface. Remove the bowl with the dough wearing oven mitts, and transfer the bowl onto the towel.

Scrape the dough from the bowl and knead it using a spoon, until it forms a dough ball, 5 minutes or so.

Transfer the dough onto a clean surface. Note, do not add any flour onto the surface or dust your hands with it. Knead the dough using your hands until it’s smooth, 5 minutes or so. The dough will soften once done.

Form the dough into balls - Measure 25 grams of dough (about 1 round tablespoon) and use your hands to roll it into a ball. Place the dough balls into a container and cover. Chill in the fridge until the custard is ready to use.

You can keep the dough and the custard filling refrigerated for a couple of hours, up to overnight, until ready to assemble. The dough will become a bit stiff if you chill it overnight. If you want the freshest taste, you should assemble the mooncakes the same day you make the dough and filling.

Once the custard is fully chilled, use a spatula to mix the custard again to even out the texture. This step will soften the custard a bit, but make it easier to scoop and shape.

Form the custard into balls - Measure 25 grams of filling (about 1 round tablespoon) and use your hands to press and roll, until it forms a ball. I highly recommend wearing disposable gloves to help with this process, so the custard doesn’t stick to your hands.

Transfer the filling balls into a plate and wrap it. Chill for another 30 minutes.

Place the dough ball on a clean working surface. Use a rolling pin to roll it into an even, thin, round disc that is about 4” (9 to 10 cm) in diameter. Carefully remove it from the surface onto your palm.

Place a custard ball in the center of the wrapper. Use your other hand to gather the wrapper onto the top of the custard filling. The dough sheet will start to form pleats and create a thicker layer. Try to pinch the extra dough together using your fingers, and pinch off the dough. The process will keep the mooncake skin even and thin, to create a better mouthfeel. Once done, place the mooncake onto a plate, pleated-side-down. Loosely cover it with plastic wrap to prevent them from drying out. Repeat the process to wrap the rest of the mooncakes.

Install the pattern plate into the mooncake mold, with the pattern side facing downward. If you’re using the round shape, you can twist the lever of the mold so the pattern plate will snap onto the lever. It’s not required but it makes the process a bit easier.

Dust the mooncake with a very thin layer of cornstarch. (*Footnote 1)

Carefully place the wrapped mooncake balls into the mold, smooth surface against the pattern plate.

Place the mold onto a clean, flat surface. Gently press the lever until the dough is against your table surface. Hold it for at least 30 seconds. It will help the pattern to form. Once done, push the lever to release the mooncake. Repeat the process to mold all the mooncakes.

The mooncakes are ready to eat!

Transfer the mooncakes into an airtight container. Store them in the fridge for 3 to 4 days. To enjoy the mooncakes with a better texture, transfer them to your kitchen counter and wait for them to return to room temperature. You can eat the chilled mooncakes, but the skin will be a bit stiff.

Note, do not freeze the mooncakes. This will change the texture of the custard and make it very grainy.