Mantou (Resep Terbaik)

Bahan-bahan (8 porsi)

• 1/2 tablespoon yeast
• 100 ml warm water
• 1/2 teaspoon sugar
• 75 g (2¾ oz) sweet potato ((or "yam" in the United States))
• 250 g (9 oz) all purpose flour
• 2 tablespoons sugar
• 1 tablespoon oil
• 1 tablespoon oil