Preheat the oven to 220°C (425°F) and line a baking sheet with parchment or lightly grease it.
In a large bowl combine the Self-Raising Flour, Baking Powder, Salt and Caster Sugar.
Cut cold Unsalted Butter into small cubes and rub it into the dry ingredients with your fingertips (or pulse briefly in a food processor) until the mixture looks like fine breadcrumbs.
Stir together the Whole Milk and Lemon Juice and let sit for 1–2 minutes to slightly thicken (this gives the dough a gentle tang).
Make a well in the dry mix, pour in the soured milk and fold gently with a spatula or wooden spoon until a soft, slightly sticky dough just comes together — don’t overwork it.
Turn the dough out onto a lightly floured surface and use Flour to dust as needed; pat or roll the dough to about 2 cm (¾ in) thickness and cut into rounds with a cutter.
Place the scones on the prepared baking sheet, brush the tops with beaten Egg for a glossy finish (or a little milk if you prefer), and bake for 12–15 minutes until risen and golden-brown.
Cool briefly on a wire rack, then split the scones and serve warm with generous spoons of Clotted Cream and Strawberry Jam.
