How To Make Matcha Swirl Bread 

1. For the Old Dough:
1. Combine milk, yeast and sugar in a mixing bowl. Then add in bread flour and mix with hand until become a soft dough.  Roll into a ball and place in a greased bowl.  Cover with cling film and let it proof 1 hour in room temperature (28C - 29C).  
2. After 1 hour, place into the refrigerator overnight for at least 12 hours or up to 16 hours. Fridge temperature 2C - 4C. The next morning, take out the old dough from refrigerator to return to room temperature 30 minutes before using.  You can also use directly from the fridge if you forget to take out earlier.
3. If you don't plan to bake the next day, after 1 hour fermentation, shape it into a ball and wrap it in cling wrap or place it in a ziplock bag. Store it in the freezer for 1-2 months.  Take it out 30 minutes before using to defrost.
2. For the main dough:
1. Put all ingredients (except butter and matcha powder) including old dough (I usually tear the old dough slightly) into a bowl of stand mixer.
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 at low speed #2 for about 3 minutes or until the dough comes together and elastic.  
3. Change to hook attachment,  add in butter and continue kneading for 10 - 12 minutes at low speed #2 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. After kneading, divide dough into 2 equal portions.  Shape one portion into a ball and leave in a bowl and cover. 
5. Return another portion into the bowl of stand mixer and sift in matcha powder.  Add 1 - 2 teaspoons of milk and knead again at medium speed until well mixed.  Shape into a ball and leave in a bowl and cover.
3. 1st Proofing:
1. Let the dough rise in a warm place for 60 minutes or until double in size.  
4. Shaping:
1. Punch down each dough to release the air.
2. Move the plain dough to a floured or oiled surface, shape it into a ball, and let it rest for 10 minutes. Do the same with the matcha dough.
3. Roll the plain dough into a rectangle with a rolling pin. Repeat with the matcha dough.
4. Place one dough on top of the other, press them together with your palm, and flatten slightly with the rolling pin.
5. Roll them up tightly from the shorter side to form a log and pinch the seam to seal it.
6. Place the dough in a loaf pan.
5. Final Proofing:
1. Let it rise for another 30 - 45minutes or until the dough reaches about 1 cm below the rim of the pan.  This took about 40 minutes at a room temperature of 29°C - 30°C.
6. Baking:
1. Preheat oven at 180C - 190C (top & bottom heat) or 170C - 180C (fan-forced) for 15 minutes before baking.
2. Brush with egg wash.
3. Bake in a preheated oven for about 30 minutes, or until golden brown.  If it is browning too quickly, cover the top loosely with aluminium foil.
4. Remove bread from oven then remove the bread from the pan.  Let it cool on rack completely before slicing.