Preheat your oven to 220°C (425°F/Gas Mark 7). Line a large baking sheet with parchment paper or a silicone baking mat to prevent the scones from sticking to the bottom.
Sift the self-raising flour into a large mixing bowl. Add the chilled, cubed butter. Use your fingertips to rub the butter into the flour until the mixture resembles fine breadcrumbs. Try to work quickly so the heat from your hands doesn’t melt the butter.
Stir in the caster sugar. Make a well in the center of the mixture and pour in the milk. Use a blunt knife or a spatula to fold the ingredients together until a soft, slightly sticky dough forms. Avoid over-mixing, as this will make the scones tough.
Turn the dough out onto a lightly floured surface. Gently fold the dough over a few times just until it is smooth. Pat it down with your hands until it is about 2.5cm (1 inch) thick. Use a 6cm round cutter to stamp out circles. Press straight down and lift up without twisting the cutter to ensure a straight rise.
Place the scones on the prepared baking tray. Brush the tops with a little extra milk for a golden finish. Bake for 10 to 12 minutes until they have risen significantly and the tops are a light golden brown. Transfer to a wire rack to cool slightly.