Preheat the oven to 220˚C/425˚F/Gas Mark 7.
Place the flour and salt in a large bowl. Cube the butter and work into the flour using a pastry blender or your fingertips until the mixture resembles fine breadcrumbs.
Add in the sugar and sultanas and mix well.
Make a well in the centre and add all of the milk. Mix together roughly to a dough using a table knife.
There are a couple of secrets to the perfect scone and the first is to not handle the mixture too much. Bringing the dough together with a knife will stop you manhandling it!
Tip out this rough dough onto your work surface and using your hands bring together lightly into a more consistent dough.
Instead of using a rolling pin and battering the life and lightness out of your dough pat it down into a rectangular shape about 1" thick.
Make a small pile of flour on the worksurface by the side of your dough and put your cutter into it wriggling it about a bit. I use a 2" plain cutter - I like my scones to be of a decent size - no piddling little measures here!
Cut out the scones using only a downward press - DO NOT TWIST THE CUTTER - did you get that? Twisting the cutter when forming the scones seals the sides together and they won't rise. Flour the cutter between each on the little pile of flour as before.
Prepare a baking tray by greasing or use a non-stick liner.
Crack an egg into a shallow bowl and whisk to make the egg wash, add a splash of milk if desired. Fill another shallow bowl with caster sugar.
Take each scone in turn and dip top down into the bowl of egg wash and then into the bowl of sugar coating the top of each. Place onto the baking tray spaced well apart.
Bake them in the oven for 12-14 minutes.
Remove from the oven and allow to cool on a wire rack.
In the oven the egg wash and sugar with have formed the most delicious sugar crust.