Preheat & Prep: Preheat your oven to 220°C. Lightly grease a baking sheet.
Combine Dry Ingredients: Measure the flour and baking powder into a large bowl. Add the chilled butter cubes.
Rub in the Butter: Use your fingertips to quickly and lightly rub the butter into the flour mixture until it resembles fine breadcrumbs. Stir in the sugar.
Add Wet Ingredients: Crack the egg into a measuring jug, lightly beat it, and then make it up to 125ml (4 fl oz) with milk.
Form the Dough: Keep about 1 tablespoon of the egg/milk mixture aside for glazing. Stir the rest of the liquid into the flour mixture using a round-bladed knife, mixing quickly to form a soft, slightly sticky dough. Do not overmix.
Shape & Cut: Turn the dough onto a lightly floured surface and knead it very lightly just to bring it together. Gently roll or pat it out to a thickness of about 1.25cm (½ in). Use an 8cm (3in) fluted cutter to stamp out rounds, pushing the cutter straight down (do not twist) to ensure a good rise. Re-form and cut the remaining dough.
Bake: Place the scones on the prepared baking sheet, spaced slightly apart. Brush the tops with the reserved egg/milk mixture to glaze.
Cook: Bake for about 10-12 minutes, or until they are well-risen and a pale golden-brown colour.
Cool & Serve: Remove from the oven and transfer to a wire rack to cool slightly. Scones are best served warm.