Sift the cake flour and baking powder into a bowl. Add sugar and salt, and mix well.

Cut the cold butter into small cubes and add to the dry mixture. Use your hands or a scraper to crumble the butter into the mixture until it resembles coarse crumbs.

Add the egg and milk to the mixture and gently combine until just incorporated.

Fold in the dried blueberries or raisins, mixing lightly.

Scoop the dough onto a baking tray using a spoon or scoop. Brush the tops with any leftover egg mixture.