Combine warm milk, warm water, sugar, and yeast in a bowl. Let sit for 5 minutes until foamy.

Add flour, baking powder, salt, and vegetable oil. Mix until a dough forms.

Knead the dough for 8–10 minutes until smooth and elastic.

Place dough in a greased bowl, cover, and let rise for 1 to 1½ hours until doubled.

Divide dough into 10–12 pieces and roll each into a ball.

Flatten each ball into an oval, brush lightly with oil, and fold in half.

Place each bun on parchment paper and let rise again for 30 minutes.

Steam buns for 10–12 minutes until fluffy and cooked through.

Fill buns with desired fillings and serve warm.