Bamboo steamer (or equivalent. I've used a chafing dish with a perforated pan, and one of grandmas old umbrella-style vegetable steamer baskets)
1tbspactive dry yeast
4tbspsugardivided in half
2 ½cupsall purpose flouruse blenched flour if you want complete white buns
In the bowl of a stand mixer, combine warm water, milk, active yeast, half of the sugar and oil. Whisk together briefly, and let stand for 10 minutes until yeast is foamy.
In a separate bowl, combine flour, remaining sugar, baking powder and salt. With the dough hook attachment fixed, start the mixer on low speed and begin adding the dry ingredient mixture a little at a time, until all dry ingredients are incorporated.
Increase the mixer speed to medium and knead the dough for 3-4 minutes, until smooth and elastic. Remove the dough hook and form the dough into a ball. The dough should not stick to your fingers. Place the dough back into the bowl, cover it with plastic wrap, and set in a warm (but not hot) location and allow it to rise for 2 hours. Dough should triple in size.
Divide the dough in half. Keep one half covered in the bowl, and place the other half on a work surface. Roll into a log and divide into 8 pieces. Form each piece into a ball by rolling between your palms. Roll each dough ball until about ¼" thick. Spray the top generously with cooking spray, fold into a half moon, and place in a steamer basket lined with parchment.
Bring some water to a boil in the wok. Place the bamboo steamer over the water and cover. Steam for 10 minutes, then remove steamed buns to a baking sheet lined with parchment to cool a bit.