Combine the water, milk, yeast, 2 T sugar, and oil in a small mixing bowl. Set it to the side.
Combine the flour, 2 T sugar, baking powder, and salt in a stand mixer.
Turn your stand mixer on a low setting and slowly begin adding your wet ingredients to your dry.
Once, all of the ingredients are incorporated together, use your dough hook to continue kneading for about 5 minutes.
Form dough into a ball and place back into the stand mixer bowl and cover with saran wrap. Let it rise in a warm place for 2 hours.
After it has risen, place the dough ball on a clean, lightly floured working surface. Using a rolling pin, roll your dough out until it is about 1/4 inch thick.
Using a circle cutter or a circular drinking glass, cut as many circles as you can out of your dough.
Ball up whatever dough is left over, and roll it out and cut your circles shapes out once again, repeating until you have no dough left.
Pour some olive oil into a bowl and and have a food brush on hand.
Brush the entire surface of your bao circle with olive oil, and fold it in half, forming it into a bun. Repeat for all bao circles.
Cover and let it rest for an additional 1 hour.
After the dough is rested, place your steamer into a large pot, wok, or cast iron pan of water and bring it to a boil. Make sure it isn't filled up too high with water so that the bottom tier of your steamer does not fill with water.
Once water is boiling, place your bao buns into the steamer and steam for about 10 minutes.