Make the dough:

1. In a medium bowl, sift the flour. Then add the water, sugar, vegetable oil, baking powder and yeast to the bowl. Mix with a wooden spoon until well combined.
2. Knead the dough with your hands for about 5 minutes. The dough shouldn’t be sticky. If it’s a little sticky, add a little bit of flour. Keep kneading and folding and make a ball.
3. Cover the dough with a wet towel and let it rise on the counter for about 20-30 minutes.

Make the filling:

1. While the dough is rising, make the filling. Heat a frying pan at medium-high heat. Add the vegetable oil and let it get hot. Add the diced onions and minced garlic to the pan. Sauté for about 2-3 minutes. Then reduce to medium heat.
2. Add in the hoisin sauce, soy sauce, oyster sauce, granulated sugar, sesame oil, and salt. Stir well to combine. Whisk together the water and cornstarch in a small bowl. Slowly add to the pan, stir to combine, and let it simmer for about 2 minutes, until the mixture has thickened.
3. Add the ground pork to the pan, chopping up the pieces to make sure it’s completely cooked. This can take about 7-10 minutes. Remove from heat once the meat is fully cooked and let it cool completely.

Make the dumplings:

1. Sprinkle some flour onto your worktable and place the risen dough on top.
2. Fold and flatten with a rolling pin a few times until you have a long rectangle. Then, roll up the dough and cut it into 16 even pieces.
3. Using a rolling pin, roll out each individual piece of dough until you have a 3-inch circle.
4. Put 1-2 tablespoons of filling in the middle of the dough circle and start folding the edges towards each other, all the way around until you’ve closed the bun.
5. Line a bamboo steamer with parchment paper punched with holes and place the buns in the steamer. Make sure not to overcrowd them and leave about 1-inch spaces between them.
6. Add about ¼ inch of water to a heavy wok and bring to a boil. Place the bamboo steamer (with the lid on) into the wok and let it steam for about 12-14 minutes. If you aren't using both steamer trays you will need to repeat this step for the next batch. (Make sure there is always water in the wok. You can add a little more if all of the water has reduced.)
7. Turn off the heat and let the buns rest for 5 minutes before opening the lid. Missing this step will cause the buns to collapse. Remove from the steamer and enjoy while warm!