Begin by washing and peeling the sweet potatoes. Slice them into even pieces to ensure they cook evenly.

Place the sweet potato slices in a steamer and steam over medium-high heat for 15-20 minutes, or until they are soft and fully cooked.

Measure 400g of the cooked sweet potatoes and transfer them to a large mixing bowl.

While the sweet potatoes are still warm, add 1 tablespoon of granulated sugar. Using a fork or potato masher, mash the sweet potatoes until smooth and lump-free.

Allow the sweet potato puree to cool to room temperature. Once cooled, add the instant yeast (5g) to the mixture and stir until well combined.

Gradually add 500g of all-purpose flour to the sweet potato mixture. Mix until the dough starts to come together. The dough should be soft and slightly sticky. Depending on the moisture content of the sweet potatoes, you may need to adjust the dough consistency:

If the dough is too dry, add a little water, one tablespoon at a time.

If the dough is too wet, add more flour, a tablespoon at a time.

Add 15g of corn oil to the dough and knead until the oil is fully incorporated.

Continue kneading the dough for 3-5 minutes until it becomes smooth, elastic, and slightly soft to the touch.

Cover the dough with plastic wrap or a damp cloth. Let the dough rise in a warm place for 30-45 minutes, or until it has doubled in size. The rising time may vary depending on the room temperature.

Once the dough has doubled in size, transfer it to a lightly floured work surface. Knead the dough briefly to release any air bubbles.

Divide the dough into 12 equal portions (you can use a kitchen scale for accuracy). Shape each portion into a smooth, round ball by tucking the edges underneath and rolling them gently between your palms.

Pinch the bottom of each ball tightly to seal and roll the balls slightly taller to form the classic mantou shape.

Place the shaped dough balls onto small squares of parchment paper to prevent sticking.

Set the dough balls in a steamer (without turning on the heat) and let them proof for an additional 15 minutes. You can place the steamer over warm water to aid in the rising process.

After the second rise, turn the heat to medium-high and steam the mantou for 15 minutes. Make sure to keep the lid on during steaming.

Once the steaming time is up, turn off the heat but leave the mantou in the steamer for an additional 3 minutes. This resting period helps prevent the mantou from collapsing due to the sudden temperature change.

Carefully remove the mantou from the steamer and let them cool slightly before serving.