Preheat the oven to 180°C (356°F).
Mix flour, baking powder, sugar, and salt in a bowl.
Cut cold butter into small cubes, add to the bowl, and mix by hand until the mixture becomes crumbly.
Add green tea powder and mix again.
Add milk and egg, kneading the dough into a single lump.
Flatten the dough and cut into triangles.
Place on a parchment-lined baking tray and bake for 18-20 minutes.