Step-By-Step Instruction

1. Yudane Dough:
1. Add bread flour in a bowl, pour the boiling water and mix well with spatula or spoon until no dry flour.
2. Cling film and place in the fridge for at least 4 hours or overnight.  I prepared the night before.
3. Take out from the fridge 30 minutes before using to return to room temperature.
2. Sweet Stiff Starter 
1. Dilute starter with water, stir in sugar and mix in bread flour to become a dough.  I usually mix with plastic scrapper then mix with hand to make into a ball.  Please use stand mixer with paddle attachment to mix if you find hard to mix with hand.
2. Cover and let it ferment until tripled. I prepared a night before and leave it in aircond room (approximately 24 - 25C room temperature) overnight until tripled.  It took about 8 - 9 hours depending on your starter.  It should take around 4 - 6 hours to get triple at room temperature at 28C - 30C. 
3. However, if you feed your starter with milk, the starter will take longer time to proof and very much depend on your stater.  Mine took about 9 - 10 hours to proof overnight.  And the starter did not rise until triple somtimes in size compared feeding with water.  It rose almost 2.5 to 3 in size.  
3. Main Dough:
1. Put all ingredients (except butter and raisins), including all the stiff starter and yudane dough into a bowl of stand mixer.  I usually torn the stiff starter and yudane dough into pieces first.
2. Slightly combine the mixture by hand with the paddle attachment before turning on the machine so that the flour will not splash out.  Using the paddle attachment, mix for 2 minutes or until all incorporated.  This step is critical to prevent  an uneven mixed dough as the stiff starter is rather hard and a dough hook may not be able to mix it well enough.
3. Change to hook attachment and knead for another 3 minutes or until the dough comes together. Add in butter and continue knead for 10 - 12 minutes or until reach window pane stage.  The whole kneading process, I stopped few times to scrape down the dough from the hook to be sure it is evenly kneaded and also to prevent the motor from overheating.
4. Add in rinsed raisins and continue kneading for about a minute until the raisins evenly mix in the dough.  
4. 1st Proofing/Resting:  
1. In the same bowl, let the dough rest for 15 - 60 minutes. Keep it covered with clingfilm or use a lid.  This dough I rested for 45 minutes and the dough rose slightly in 45 minutes. 
5. Shaping:
1. Transfer the dough to a clean floured surface then divide dough into 16 equal portions or 9 equal portions (if you prefer bigger buns).  Please use a kitchen scale if you want to be exact.  
2. Form each portion to a ball.  Please watch the video here "How to shape bun"
3. Place place bun onto the baking pans lined with non-stick baking paper. 
6. Final Proofing:
1. Let the buns proof at a warm place until the dough rise double in size. This one took approximately 3 1/2 hours at at room temperature of 30C.  The duration of proofing depends on your ambient temperature and the starter.
7. Flour Paste for The Cross:
   1. Whisk flour, water and oil together until become a thick pipeable paste.  Transfer the paste to a pipping bag and snip the tip off or use round nozzle if you have. Set aside.  If you do not have a piping bag just used a clean plastic bag and snip the tip/corner off.
8. Baking:
1. Preheat oven at 190C (top & bottom heat) or 170C (fan-forced) for 10 - 15 minutes.
2. Brush with egg wash.
3. Pipe a cross on each bun with the prepared paste. 
4. Bake in a preheated oven for 15 - 20 minutes, or until golden brown.  For my oven, I make sure I did not bake more than 20 minutes as the buns will become dry easily by the next day even though yudane method is used. 
5. Remove buns from oven and let them cool on rack.  Brush buns with sugar glaze if you like once out from oven.