In a large bowl, whisk together flour, yeast, sugar, baking powder, and salt.

Gradually add warm water and vegetable oil to the dry ingredients, mixing until a shaggy dough forms.

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

Lightly oil a clean bowl, place the dough inside, cover with plastic wrap, and let it rise in a warm place for 1.5 to 2 hours, or until doubled in size.

Once risen, punch down the dough to release air. Transfer it to a lightly floured surface and roll into a log.

Divide the log into 12 equal pieces.

Take one piece, flatten it slightly, and roll it into an oval shape (about 4-5 inches long and 3 inches wide).

If making filled buns, place about 1-2 tablespoons of your desired filling in the center, then fold and pleat the edges to seal. If making plain buns, simply fold the oval in half, creating a crescent shape.

Place each shaped bun on a small square of parchment paper.

Arrange the buns in a steamer basket, ensuring there's space between them. Cover the steamer and let the buns rise for another 30-45 minutes, or until visibly puffy.

Bring water in a pot or wok to a boil. Place the steamer basket over the boiling water, ensuring the water doesn't touch the buns.

Steam for 10-15 minutes on medium-high heat. Do not lift the lid during steaming.

Once steamed, turn off the heat and let the buns rest in the covered steamer for 5 minutes before removing. This prevents them from deflating.

Serve warm with your favorite dipping sauce or enjoy as is.