Char Siu Bao (Roti Babi Kukus)

Bahan-bahan (16 porsi)

• 1/2 tablespoon cooking oil
• 1 small yellow onion (diced)
• 250 g (9 oz) char siu (diced)
• 1 tablespoon soy sauce
• 1 tablespoon oyster sauce
• 1 teaspoon sugar
• 1 teaspoon sesame oil
• 1 -2 drops red food coloring (optional)
• salt (to taste)
• 1 1/2 tablespoons cornstarch
• 150 ml water
• 280 g (10 oz) low-protein flour ((Hong Kong flour), cake flour or all-purpose flour)
• 100 g (3½ oz) wheat starch
• 90 g (3 oz) powdered sugar
• 8 g (⅕ oz) active dry yeast (or instant yeast)
• 160 ml lukewarm water
• 1/2 teaspoon Chinese white vinegar (or lemon juice, optional)
• 30 g (1 oz) vegetable oil
• 10 g (¼ oz) baking powder
• 10 ml cold water