Step 1

In a small bowl, whisk together the water, yeast and sugar until the yeast dissolves. Let the mixture sit until the yeast starts to get foamy and bloom, 4 to 6 minutes. Stir in the oil and set aside.

Step 2

Meanwhile, sift the bread flour, salt and baking soda together. Add the yeast mixture to the dry ingredients and stir using a rubber spatula. If the dough looks sticky, add 1 additional tablespoon of flour at a time until it is less sticky.

Step 3

Turn the dough onto a lightly floured work surface and knead until smooth. Cover the dough with a damp kitchen towel and let the dough rest until it has doubled in size, 1½ to 2 hours. Punch the dough down to flatten it.

Step 4

Portion the dough into balls that are 2 inches in diameter and let rest for 5 minutes. Flatten each ball into a disk 3 inches in diameter.

Step 5

Fill the buns with your filling of choice and wrap by gathering the edge and twisting slightly. Cover with a damp kitchen towel to keep the bao from drying out.

Step 6

Place the buns in a steam basket lined with parchment paper and steam until the buns have expanded, 7 to 9 minutes. Serve.