In a large mixing bowl, combine the all-purpose flour, sugar, and instant yeast. Gradually pour in warm milk, mixing until a shaggy dough forms.

Knead the dough on a floured surface for 8 to 10 minutes until it becomes smooth and elastic.

Incorporate the vegetable oil into the dough, cover with a damp cloth, and let it rise in a warm place for 1 hour, or until doubled in size.

While the dough rises, heat sesame oil in a skillet over medium heat. Add minced garlic and grated fresh ginger, sautéing for about 30 seconds until fragrant.

Stir in the finely chopped beef along with soy sauce, hoisin sauce, and rice vinegar. Simmer the mixture for 10 to 15 minutes until the beef is thoroughly cooked and the sauce has thickened slightly.

Create a cornstarch slurry with water and mix it into the filling, then let it cool completely.

Once the dough has risen, punch it down and knead in the baking powder.

Divide the dough into 14 to 16 equal pieces, shaping each into a ball.

Roll each piece into a disc about 4 inches wide, then spoon a tablespoon of the cooled beef filling into the center.

Pleat and pinch the dough around the filling to seal. Place each bun seam-side down on parchment paper.

Prepare your steamer by bringing water to a boil, ensuring it won’t touch the buns.

Place the buns on parchment in the steamer basket, cover them, and let them rest for 10 minutes.

Steam the buns for 12 to 15 minutes over high heat until they puff up and appear glossy.

Once cooked, let the buns sit for 2 minutes before serving.