Mix all ingredients except butter and mix at low speed for 2 minutes. Increase the speed to high and mix for 3 minutes.
Add in butter and continue mixing for 2 minutes at low speed. Increase the speed to high and mix for 3-5 minutes until a smooth and pliable dough is formed.
Cover the dough with a damp cloth and rest for 30 minutes.
Divide the dough to 30g each, cover and rest for 20 minutes.
Round the dough pieces and place it a sequence of 4 pieces of dough by 3 pieces in a greased square baking tin or any desired shape of baking tin.
Cover and place in a warm place and proof the buns for 60-70 minutes.
After proofing, egg wash the surface of the buns. Using a pair of scissors cut a slit down the middle of each bun, pipe softened butter on the center of slit and sprinkle sugar on butter.
Bake at 220°C for 8-10 minutes until buns are golden brown.