Wash the pumpkin thoroughly. Carefully cut it into halves, remove the seeds and stringy pulp, and then peel off the tough skin. Cut the flesh into small, 2cm cubes.

Place the cubes in a steamer basket. Bring water in the steamer to a boil, then reduce to medium heat and steam the pumpkin for 15 minutes, or until the cubes are very tender and can be easily pierced with a fork or chopstick. Take the steamed pumpkin out and place it in a large bowl.

While the pumpkin is steaming, generously grease the inside of your chosen mold with a little extra corn oil, making sure to coat the bottom and all sides.

Using a spoon or a fork, thoroughly mash the steamed pumpkin while it is still warm. Mash it until it is completely smooth and free of any lumps. You should have exactly 200g of pumpkin purée.

In a large mixing bowl, combine the 200g of warm pumpkin purée, 40g of white granulated sugar, and 230g of water. Whisk until the sugar is dissolved and the mixture is smooth.

Add the 8g of glutinous rice flour and the 160g of tapioca starch to the bowl. Whisk very vigorously and quickly to combine everything and to prevent the tapioca starch from forming lumps. The batter should be completely smooth.

Finally, pour in the 20g of corn oil. Continue to whisk for about another minute until the oil is fully incorporated and the surface of the batter looks glossy.

Pour the smooth batter into your prepared, oiled mold. Gently tap the mold on the counter 3-5 times to release any air bubbles trapped in the batter.

Prepare your steamer and bring the water to a rolling boil. Carefully place the mold into the steamer. Cover the steamer and maintain a medium heat. Steam for 30 minutes.

If your mold is very shallow (less than 3cm deep), check at 25 minutes. If it is very deep, you may need to steam for 35 minutes. To check for doneness, insert a clean chopstick into the center of the nian gao. If it comes out clean, with no wet batter sticking to it, it is done.

Immediately after removing the nian gao from the steamer, sprinkle the top evenly with the 15g of toasted white sesame seeds.

Place the entire mold on a cooling rack and allow the nian gao to cool completely to room temperature. This is a mandatory step that will take about 1 hour. Do not attempt to remove or slice it while warm, as it will be too soft and sticky.

Once completely cool, run a thin knife around the edges of the mold to loosen the nian gao. Invert the mold to release it onto a cutting board. Use a sharp knife, lightly moistened with water, to slice it into pieces. Wipe the knife clean between cuts for neat slices.