Dough: in a bowl, combine water, sugar and yeast together. Mix well to combine and cover with a plate, let sit for 5 minutes or until the mixture is foamy on the top. Add flour, salt and oil and mix well until all the water is absorbed. Pour mixture onto a clean surface and knead for 5-10 minutes or until the dough is smooth. Place dough ball back into the bowl and cover with tea towel for 45 min – 1 hour.
Filling: in a pan over medium-high heat, saute with a bit of oil the onion, shallot, mushroom and carrots until soft. Add in the remaining ingredients and stir fry until the cabbage is wilted and the mixture is mostly dry. Season generously with pepper, set aside to cool.
Rolling: divide dough into 2 equal pieces and put 1 back into the bowl with the tea towel while you work on the other piece. Roll piece into a log and divide into 8-10 pieces, depending on how big you want the buns to be.
While you work on one piece, cover the rest to prevent drying. Shape it into a ball and with a miniature rolling pin, roll it into a circle (approx.. ¼ cm thick). Place approx. 1 tbsp of filling into the centre of the circle and create pleats around the edges to form a bao bun. (see video above for visuals). Repeat for the remaining dough pieces.
Frying: place a frying pan, with enough oil to cover the base of the pan, over medium heat. Place the bao buns into the oil and fry until the bottoms are golden brown. Once the bottoms are crispy, drop the heat by a bit, then pour approx. ¼ - ½ cup of water (enough to cover the base of the pan) into the pan and immediately cover with a lid, be careful it’s going to splatter so do it quickly. Let it steam for 8-10 minutes, uncover and let the water evaporate off. Fry for an extra 5 minutes to crisp up the bottoms again.
Garnish with sesame seeds and green onion slices.