Dissolve yeast in warm water in a bowl. Add milk, butter, and sugar; mix to combine. Add flour and mix to form a dough.

Knead dough until a uniform ball forms. Cover and allow to rise in a warm place until doubled in size, approximately 30 minutes.

Cook ground pork with garlic, ginger, salt, and black pepper in a skillet over medium-high heat until browned and crumbly, about 5 to 7 minutes. Drain and set aside.

Prepare a steamer by filling a saucepan with water just below the steamer insert. Bring water to a boil.

Divide the dough into 16 equal pieces. Roll each into a ball and flatten into a thin circle.

Place 1 tablespoon of the prepared filling in the center of each circle of dough. Pinch the edges together at the top to seal.