In a large mixing bowl, combine flour, sugar, salt, and active dry yeast. Gradually add warm milk until a soft dough forms.

Transfer the dough onto a floured surface and knead for about 10 minutes until smooth and elastic.

Place the kneaded dough in an oiled bowl, cover, and let it rise in a warm area for about 1 hour.

Once risen, punch down the dough, divide it into 12 pieces, roll into balls, and flatten into circles.

Prepare the filling by cooking pork belly/chicken/tofu with soy sauce and sriracha until cooked through, about 5–7 minutes.

Place a spoonful of filling on each dough circle, fold to seal, and steam for about 15 minutes.