Preheat the oven to 180°C (356°F).
In a bowl, combine cake flour, sugar, baking powder, and salt.
Add cold butter and break it into small pieces, mixing with your hands.
Add milk and egg, and gently knead the dough.
Add rinsed blueberries and carefully fold them in.
Divide the dough into even portions and place them on a baking pan.
Bake in the oven for 20–25 minutes.