Preheat the oven to 425˚F (220˚C).
In a large bowl, rub together the self-raising flour and cubed butter until you form fine crumbs.
Mix in the sugar, baking powder, and salt, and make a well in the middle.
Pour in the milk and gently mix together until just combined.
Tip the dough onto a floured surface and knead for about a minute. Be careful not to over-knead the dough.
Using a round cookie cutter or the rim of a glass, cut circles into the dough that are about 1-2 inches thick.
Place onto a baking tray lined with parchment paper and coat the tops of the scones with the egg yolk.
Bake for 12 minutes.
Serve with clotted cream and jam.
