Mix bread flour, dry yeast, sugar, and salt together.
Add warm water, milk, and cooking oil to make a dough.
Let the dough ferment for about 1 hour.
Divide the sweet red bean paste into 20g portions and roll them into balls.
Divide the dough, roll it out with a rolling pin, put the bean paste in the center, and wrap the filling.
Line a steamer with a damp cloth and place the buns on top.
Steam over boiling water for 15 minutes.