1. In a mixing bowl, combine flour, sugar, salt, and yeast.
2. Add warm water and vegetable oil, mix until a dough forms.
3. Knead the dough for about 10 minutes until smooth and elastic.
4. Cover the dough and let it rise for 1 hour or until doubled in size.
5. In a separate bowl, mix ground pork, soy sauce, oyster sauce, sugar, minced garlic, and cornstarch.
6. Punch down the dough and divide it into 12 equal pieces.
7. Roll each piece into a ball and flatten it into a disc.
8. Place a spoonful of filling in the center of each disc and pinch the edges to seal.
9. Place the buns in a steamer and steam for 15 minutes.