Mix flour and water in a small saucepan. Cook over low to medium heat, stirring continuously until it reaches 65ºC. It should have thickened to a paste at this stage, that is when you stir you can see the bottom of the pan. Remove from heat, place a cling wrap over the paste and leave until lukewarm, or room temperature, before using. (Alternatively if you don’t have a thermometer, cook as before until it just starts to thicken, then continue to cook for about 1 more minute before removing from heat.) This water roux can be kept in an airtight container after cooling in the refrigerator for 1 day if not used immediately. However DO NOT USE if it turns grey in colour, that means it has gone bad.
For the Bun Dough:.
Sift bread flour, plain flour, custard powder, milk powder, caster sugar and salt onto the working surface. Add instant dry yeast and mix well. Form the flour mixture into a well. Add lightly beaten eggs and lukewarm water roux and mix inches Gradually add just enough lukewarm water to form into a slightly sticky, soft dough. Knead for 10 minutes until smooth and elastic. During hand kneading, the dough also needs to be thrown onto the working surface once every few minutes between kneading to improve the dough structure. (I usually just pick up the dough to about head-high and throw it down onto the working surface 10 to 20 times every few minutes between kneading.).
Knead in butter until incorporated. Form the dough into a round ball and let it rise until double in size in a large greased bowl, cover with cling wrap (should take about 1 hour in warm weather, longer in winter months). To test if the dough has risen properly, dip a finger into bread or plain flour and poke down into the centre of the dough as far as your finger will go and pull out again – the hole should remain if it is ready. If the dough springs back, then it is not ready, continue to prove further.
Punch down, knead briefly. Then divide into 16 equal portions. The easiest way is to first divide equally into 4 larger portions first, then divide each of these again into quarters each. Form each into balls and let rest for 10 minutes.
Shape and fill as desired to make into buns of your choice. Place all finished buns on a greased baking sheet, lightly cover with cling wrap, and let rise until double in size (about 1 hour in warm weather, longer in winter months).
Bake in preheated 190°C oven for about 12-15 minutes.