In a mixer bowl, add the warm water, oil, yeast and sugar. Let sit for 1 minute, until the yeast begins to bubble a bit. Next, add in the flour, baking powder and salt mix with the paddle attachment on low for 2 to 4 minutes. If the dough sticks to the sides of the bowl Add more flour, a tablespoon at a time. Change to a dough hook and knead for 4 to 6 minutes on low speed, until dough is smooth and is not sticking to the sides of the bowl.
Tip the dough onto a lightly floured work surface and knead for 10-15 minutes, or until smooth. Place in a lightly oiled bowl, cover with a damp cloth and leave to rise for 2 hours or until doubled in size.
Tip the dough out onto a clean work surface and punch it down. Flatten the dough with your hands, then sprinkle over the baking powder and knead for 5 minutes.
Roll out the dough into a long sausage shape, about 3 cm thick, then cut into pieces that are about 3cm wide.
In the palm of your hand, roll each piece of dough into a ball. Use a rolling pin to roll out each ball, into an oval shape about 3-4mm thick. Brush the top with a little cooking oil. Fold over one side of the oval. Place bun on a parchment paper square, transfer the prepared buns to a baking tray lined with baking parchment, cover with a clean tea towel or lightly oiled cling film and leave to prove in a warm place for 1 hour and 30 minutes or until doubled in size.
Heat a large steamer over a medium-high heat. Steam the buns for 8 minutes until puffed up (you’ll need to do this in batches). Fill with the barbecue pork and pickled cucumbers and cilantro.