Measure the flour into a basin, add the yeast and baking powder and mix to combine. Next, pour in the milk or water and stir with chopsticks until the dough starts to come together, and looks tangled and still a little dry.
Water absorption will differ depending on the environment, but the dough needs to be a little dry at this point as it will soften to the right texture when you knead it.
Bring the dough together with your hands and knead it by hand for 30-40 minutes, or you can pop it into your bread machine to knead for 10 minutes. The dough will be proved in the steamer after it is stuffed with the bean paste.
Divide the dough into the same amount of portions as you have bean paste balls. Form each portion into a round and roll it out big enough to enclose the bean paste ball with a little extra to overlap and seal the paste in. Roll the dough rounds so that they are a little thicker in the middle, and thinner around the edges as these will be overlapped to seal in the bean paste ball.
Place the dough flat in your palm, place a bean paste ball on top and scrunch the dough around it, sealing it in by pinching the edges together to enclose the ball completely. Clench your hand around it tightly, to bond the two together, being careful not to distort the nice round shape.
Fill your steamer with 5cm of water and heat on low for half a minute and turn off. Place the bean paste buns, sealed side down, on the bottom rack making sure there is plenty of clearance around each bun, so they do not stick to the sides or each other when they rise.
Cover with the lid and leave for 20-30 minutes until the buns have doubled in size. (The time is not too exact because the ambient temperature will differ depending on your environment.) Open the lid now and then to check their progress.
Once the buns have risen set your steamer rack to the high position, and steam to cook the buns for a further 15-20 minutes. Setting them higher to cook ensures the buns don’t come in contact with too much direct moisture, which would cause them to collapse.