Steamed Red Skin Buns - Mi Koo [Sponge Dough Method]

Today, I need to make some of these buns as offering for ancestral worship [my father in-law's 4th anniversary].   I was wondering how these buns will be like if I were to use the sponge dough method which usually yields very soft buns.  The buns rose beautifully and indeed very soft even on the third day.  I didn't manage to take photos of the inside as all were given to my hubby's siblings.  
The ingredients are exactly the same as in my previous posting [mi koo recipe here] and the method is as below.
Ingredients for Sponge Dough

[makes 8 pieces]

450 gm plain flour - sifted

1.5 tbsp instant yeast

250 ml water

1.  Mix all the ingredients into a soft dough.  Cover to proof for 1-2 hours.

Ingredients for Bun Dough

150 gm plain flour - sift together with baking powder

1 heaped tsp double action baking powder

150 gm castor sugar

1/4 tsp salt

2-3 tbsp coconut milk

1 heaped tbsp vegetable shortening

1 tsp rose pink colouring mix with 100 ml water for brushing bun on skin

8 pieces of greased proof or parchment paper [3 inches x 5 inches]

1. Mix bun dough ingredients [except shortening] to sponge dough until well combined.   Knead until soft and smooth, then add in shortening.  Continue to knead until dough is smooth and pliable.  Shape dough into a round ball.  Cover to proof for 30 minutes or until double in size.
2. Remove dough onto a floured board.  Punch down dough to release air then roll out into a long log and cut into 8 equal pieces [about 150 gm/piece]. Form each piece into a smooth round ball then press roll from the centre to form an oblong shape dough. Put dough onto a piece of paper. Complete the same for the rest. Leave to proof till double in size [about 30 minutes]. Before steaming, brush dough with rose coloured [pink] water.
3. Heat enough water on high heat in wok. When water is boiling, put steamer [I use 2 x 14" bamboo steamer] over the water and steamed for 20 minutes. Off heat and leave steamed buns in steamer [covered] for about 3 minutes before uncovering to remove buns to cool on rack. The purpose is to get a smooth skin bun. If using other steamers be careful of water vapour that may drop onto the buns.
4. Serve buns warm with a hot beverage.

Proofed buns before steaming

Note:

These buns can be:

• stored in plastic bag and kept in the freezer for months.  Just thaw to room temperature and steam for 10 minutes before serving or
• sliced and spread with butter or
• fried with beaten egg like french toast or
• wrap with sliced roast pork.