In a bowl, combine warm water and sugar, then sprinkle in the yeast. Let it sit for about 10 minutes until foamy.

Add oil, flour, cornstarch, baking powder, and salt. Mix until a shaggy dough forms.

Transfer to a lightly floured surface and knead for 8–10 minutes until smooth and elastic.

Place the dough in a greased bowl, cover with a damp towel, and let rise in a warm area until doubled in size, about 1 hour.

While the dough is rising, dice the char siu pork into small cubes.

In a skillet over medium heat, warm the oil and sauté the garlic until fragrant.

Add the pork and stir in the oyster sauce, soy sauce, hoisin, gochujang sugar, and five spice powder.

Cook for 2–3 minutes, then add the cornstarch slurry to thicken the mixture.

Once the filling becomes glossy and slightly sticky, remove from heat and stir in sesame oil. Let the filling cool completely before using.

Once the dough has risen, punch it down and divide it into 12 equal pieces.

Roll each piece into a ball and cover with a damp towel to prevent drying.

Take one ball at a time, flatten it into a disk about 4 inches wide, keeping the center slightly thicker.

Spoon about 1 tablespoon of filling into the center. Gather the edges and pleat them up, twisting to seal the top.

Place each bun seam-side down on a square of parchment paper. Let the shaped buns rest for another 20 minutes to puff up slightly.

Bring water to a boil in your steamer setup. Arrange the buns (on their parchment squares) in the steamer, leaving enough space between each one.

Cover and steam for 12–15 minutes over medium-high heat.

Once done, turn off the heat and let the buns sit for 2 minutes before removing the lid.