Preheat the oven to 180°C (356°F).
In a bowl, mix cake flour, baking powder, sugar, and salt.
Add cold butter and mix quickly by hand until crumbly.
Add milk and egg, and gently mix until the dough comes together.
Roll out the dough thickly and cut into triangles.
Place them on a baking sheet lined with parchment paper.
Bake in the oven at 180°C (356°F) for 20 minutes.