Preheat the oven to 200°C (392°F).
In a bowl, mix cake flour, baking powder, sugar, and salt.
Add cold butter and quickly rub it into the dry ingredients with your hands.
Add milk and egg, then knead until the dough comes together.
Roll out the dough to a thickness of 2 cm and cut with a round cutter.
Place the rounds on a baking sheet and brush with egg wash.
Bake in the oven for 15 minutes.