Preheat the oven to 180°C (356°F).
In a bowl, mix cake flour, sugar, baking powder, and salt.
Grind the tea leaves into powder and add them.
Add cold butter and mix until it becomes crumbly.
Add milk and egg, then knead into a single dough.
Cut the dough into triangle shapes.
Place the dough pieces on a baking sheet lined with parchment paper.
Bake in the preheated oven at 180°C for 20 minutes.