Prepare the Dough: In two separate bowls, mix the ingredients for the white dough and chocolate dough respectively. Knead each dough until smooth, ensuring thoroughness and patience throughout the process, as it may take some time. Alternatively, you can use a kneading machine, similar to how it's done in the Steamed Piggy Buns recipe.

Roll and Stack: Roll out the white dough and chocolate dough into rectangular sheets of equal size using a rolling pin. Stack the chocolate dough on top of the white dough and spray some water on the surface.

Roll Up: Starting from one end, tightly roll the stacked dough into a log. Ensure it is rolled evenly to create a spiral effect. Then, gently roll the log to make it thinner while maintaining its shape.

Slice and Shape: Divide the rolled dough into two portions. Then, using a sharp knife, cut each portion into small mantou pieces, approximately 2cm in thickness.

Rest and Steam: Place the mantou into a steamer and cover it. Let them rise for half an hour, then steam them over cold water. Once the water boils, steam for 10 minutes.

After steaming, turn off the heat and refrain from opening the steamer lid. Allow the buns to rest undisturbed for 2 minutes.