Stir yeast and sugar into lukewarm water and stand in a warm place for about 10 minutes, or until mixture is frothy.
Sift both flours and the bread improver into the bowl of an electric mixer fitted with the dough hook. Add green tea powder, milk powder, butter, sugar, salt, egg, milk, and the frothy yeast mixture. Mix for 15 minutes, or until dough is soft and elastic.
Cover dough and leave to rise for about 1 hour, or until the dough has doubled.
Turn dough out onto a lightly floured surface; knead until smooth.
Place dough into a suitable greased mould. Lightly brush the top with egg wash and sprinkle with the cinnamon sugar and topping.
Cover and stand in a warm place for about 40 minutes, or until well risen.
Bake in preheated oven at 200°C for 15-20 minutes or until golden brown.