Prepare the Dough for Siopao Asado:

1. Activate the Yeast: In a bowl, combine the warm water and sugar. Sprinkle the yeast on top, and let it sit for about 5-10 minutes, or until it becomes frothy. This means the yeast is activated.
2. Mix the Dough: In a large mixing bowl, combine the flour, baking powder, and salt. Add the activated yeast mixture and vegetable oil, and stir to combine. You should have a slightly sticky dough.
3. Knead the Dough: Turn the dough out onto a floured surface. Knead for about 10 minutes, until the dough is smooth and elastic. If the dough is too sticky, you can add a little more flour, but be careful not to add too much.
4. Let the Dough Rise: Place the dough in a lightly oiled bowl and cover it with a clean kitchen towel. Allow it to rise for about 1 hour, or until it doubles in size.

Prepare the Filling for Siopao Asado:

1. Cook the Meat: Heat the vegetable oil in a large skillet over medium heat. Add the chopped chicken or beef, season with salt and pepper, and cook until browned and cooked through. Remove the meat from the skillet and set it aside.
2. Sauté the Aromatics: In the same skillet, add the chopped onion and garlic. Sauté until the onion is soft and translucent.
3. Make the Sauce: To the skillet, add soy sauce, hoisin sauce, oyster sauce (if using), and sugar. Stir to combine. Let the sauce simmer for 2-3 minutes to allow the flavors to meld together.
4. Thicken the Sauce: Add the cornstarch mixture (cornstarch dissolved in water) and stir until the sauce thickens into a glossy consistency. If the sauce is too thick, you can add a splash of water to reach your desired consistency.
5. Combine the Meat and Sauce: Return the cooked meat to the skillet and stir to coat it in the sauce. Cook for another 2-3 minutes. Once the filling is done, remove it from the heat and let it cool slightly.
6. Optional Add-ins: If desired, mix in chopped hard-boiled eggs or scallions to the filling for added flavor.

Assemble the Siopao Asado:

1. Divide the Dough: After the dough has risen, punch it down to release the air. Divide the dough into 8-10 equal portions and roll them into balls.
2. Shape the Siopao: Flatten each dough ball into a small circle, about 3-4 inches wide. Place a spoonful of the cooled filling in the center of each circle. If you’re using hard-boiled eggs, place a wedge of egg in the middle of the filling.
3. Seal the Buns: Gently fold the edges of the dough over the filling, pinching them together to seal. Make sure the filling is fully enclosed.
4. Prepare for Steaming: Place each bun on a small square of parchment paper to prevent them from sticking during steaming. Arrange the buns in a steamer basket, leaving enough space between each one to allow them to expand.

Steam the Siopao Asado:

1. Steam the Buns: Bring a pot of water to a boil. Once boiling, reduce the heat to a simmer and place the steamer basket over the pot. Cover and steam the buns for 20-25 minutes, or until the dough is fully cooked and the buns have expanded.
2. Check for Doneness: The siopao should have a soft, fluffy texture when done. If you’re unsure, you can open one bun to check the dough’s texture and ensure it’s cooked through.

Serve the Siopao Asado:

Once the Siopao Asado is ready, serve the buns warm. You can enjoy them on their own or with a side of pickled vegetables for a complete meal.