Preheat the oven to 180°C (356°F).
Mix cake flour, green tea powder, baking powder, sugar, and salt in a bowl.
Add cold butter and quickly rub by hand until the mixture becomes crumbly.
Add milk and egg, and form into a single dough ball.
Roll out the dough to 2cm thickness and cut into triangles.
Place scones on a baking pan lined with parchment paper.
Bake in the 180°C oven for 15–20 minutes, then cool.