Line a baking tray with baking parchment and set aside.
Add the plain flour, sugar and salt into a large mixing bowl and stir to combine.
Dissolve the dried yeast in 1 tbsp warm water, then add it to the flour together with the milk, oil, apple cider vinegar and water. Mix using a wooden spoon to form a dough.
Tip onto a floured surface and knead the dough for 5-10 minutes, until nice and smooth. Place in a lightly oiled bowl, cover with cling film and leave to rise for an hour, or until doubled in size.
Flatten the dough with your hands, and sprinkle with the baking powder. Knead for another 5 minutes then roll out into a sausage shape, about 3cm thick. Cut into 8 pieces, then roll each piece of dough into a ball.
Using a rolling pin, roll out each ball until it forms an oval shape, roughly about 3mm thick. Rub the surface of the dough with a little oil. Place a wooden spoon in the centre of each oval, and fold the dough over the spoon. Slowly pull out the spoon and place the dough onto a baking tray. Repeat until all the dough is used up.
Cover the dough with a lightly oiled cling film and leave to prove in a warm place for about an hour or until doubled in size.
Heat a large steamer over a medium heat and steam the buns for 6-8 mins until puffed up.