Preheat the oven to 220°C (200°C fan) and place a baking tray inside to heat up.
In a large bowl, combine the self-raising flour, salt, and baking powder. Add the butter and rub it in with your fingertips until the mixture resembles fine breadcrumbs.
Stir in the caster sugar and sultanas until evenly distributed.
In a jug, mix the buttermilk and vanilla extract.
Make a well in the centre of the dry ingredients and pour in the buttermilk mixture. Using a knife, gently mix to form a soft, slightly sticky dough.
Turn the dough onto a lightly floured surface. Fold it over two or three times to bring it together, then gently pat it into a round about 4cm thick.
Using a floured cutter, stamp out the scones. Press straight down without twisting to ensure an even rise. Gather and reshape any scraps as needed.
Brush the tops with beaten egg and place them onto the preheated baking tray. Bake for 15 minutes, or until well risen and golden.
