Make the Bao Buns: In a small bowl, combine the yeast, sugar, and water and stir. Set aside for 5 minutes, or until the yeast is foamy.

In a large bowl, combine the flour, baking powder, cornstarch, and salt. Add the avocado oil and the water/yeast mixture and mix to form a rough ball, adding 1 to 2 tablespoons more water if the dough is too dry. Transfer to a lightly floured surface, shape it into a ball, and vigorously knead until it’s smooth and elastic about 5 minutes.

Brush the inside of a bowl with a little oil and place the dough inside. Cover and set it aside in a warm place for 45 minutes. (Note: it won’t rise as much as other traditional yeasted doughs.)

Finish the buns: Cut twelve 4-inch squares of parchment paper and place them on a large baking sheet. Transfer the dough to a clean work surface and roll out evenly to ¼-inch thickness. Use a 3-inch food ring or drinking glass to cut out circles of dough and place them on the paper squares. Brush the tops with a little oil, then fold each circle in half and gently press down, flattening just a bit so that the halves stick together but you still have a puffy bun shape. Cover with plastic wrap and let rest for 30 minutes, until puffed.

Transfer to a bamboo steamer set over a pan with 1-inch water. Bring the water to a simmer, cover, and steam until puffed, 9 to 11 minutes. Work in batches.