In a large bowl, combine the flour, sugar, instant yeast, baking powder, and salt. Mix well.

Gradually add the warm water and vegetable oil, stirring until a dough forms.

Knead the dough on a floured surface for about 5-7 minutes until smooth.

Place the dough in a lightly greased bowl, cover with a damp cloth, and let it rise in a warm place for about 1 hour or until doubled in size.

While the dough is rising, prepare the filling by cooking the ground beef in a skillet over medium heat until browned. Drain excess fat.

Add garlic and ginger to the skillet, cooking for an additional 2 minutes.

Stir in soy sauce, oyster sauce, sesame oil, green onions, sugar, salt, and pepper. Remove from heat and let cool.

Once the dough has risen, punch it down and divide it into 12 equal pieces.

Roll each piece into a ball and then flatten it into a circle about 4 inches in diameter.

Place about 1 tablespoon of the beef filling in the center of each circle.

Gather the edges of the dough and pinch them together to seal the bun.

Place the filled buns on parchment paper squares and arrange them in a steamer basket.

Cover and let them rise for another 30 minutes.

Meanwhile, bring water to a boil in a pot or wok.

Steam the buns over simmering water for about 15-20 minutes until fluffy and cooked through.

Serve warm.