Combine flour, yeast, baking powder, sugar, and salt in a mixing bowl. Slowly add warm milk, stirring until a coarse dough forms. Let it rest for 10 minutes, then knead until smooth and elastic.

Cover the kneaded dough with a damp cloth and let it rise in a warm, draft-free area for about 1 hour, until doubled in size.

Punch down the dough, divide it into 10 equal pieces, roll each into a ball, then flatten into an oval. Brush with oil and fold to form the bun shape.

Place the shaped buns in a steamer basket lined with parchment, cover with a towel, and let them rise for another 15-30 minutes.

Bring water to a boil, steam the buns for about 10 minutes until fluffy. Rest for 5 minutes off the heat before serving.

Serve warm filled with your favorite ingredients or store leftovers in an airtight container in the fridge for up to 4 days.