Preheat your oven to 425°F / 220°C / 200°C Fan / Gas Mark 7
Sift the flour, bicarb and salt into a large mixing bowl.
Using your fingertips, rub the fat into the flour until the mixture resembles breadcrumbs.
Add sugar and stir with a spatula.
Add sultanas if using and stir again.
Form a well in the centre of the mix with your spatula.
In a small bowl beat the egg and buttermilk (or yoghurt and milk) and pour into the centre of your scone mixture.
Quickly pull the mix together - I tend to start mixing with the spatula and then go in with my hands to form the mixture into a ball.
The scone dough should be slightly sticky and soft. Add a little extra buttermilk if you find the dough a little dry.
Keep mixing to the absolute minimum.
Turn your dough onto a floured board.
Pat out your dough gently, maintaining a thick dough of 3 cm (1 ⅓ inch)
Cut out your scones using a circular pastry/cookie cutter. Push down your cutter quickly using the palm of your hand and don't twist the cutter.
For large scones use a 70 mm (2 ¾ ins) cutter or 58 mm (2 ¼ ins) for smaller scones.
Bring the trimmings back together and cut the rest of your scones. Don't over work or you will end up with tough scones.
Place your scones onto a greased baking tray.
Brush the tops of your scones with milk or egg wash.
Bake in the oven for 15 minutes (large) or 12 minutes (standard) until golden brown.
Cool on a wire rack.
Serve with jam and cream or butter.