Preheat the oven to 220C/425F/Gas 7. Grease a large baking tray with butter.
In a large mixing bowl, rub the flour and butter together, using your fingertips, until the mixture resembles breadcrumbs. Add the salt and sugar and stir until combined.
Gradually add the milk in a thin stream, stirring continuously, until the mixture comes together as a dough. (NB: You may not need all of the milk.)
Knead the dough lightly in the bowl until smooth and soft. If the mixture is too dry, add a little more milk.
Turn out the dough onto a lightly floured surface, then roll it out to a 2.5cm/1in thickness (no thinner).
Using a sharp knife, cut four 7cm/2¾in squares from the pastry and place them onto the prepared baking tray. Re-roll the remaining pastry offcuts out to a 2.5cm/1in thickness and cut two more squares. Add them to the baking tray.
Brush the tops of the scones with a little of the milk, then bake in the centre of the oven for 12-15 minutes, or until well risen and golden-brown. Remove from the oven and set aside to cool slightly.
To serve, cut the scones in half and spread with butter, then with clotted cream, then with strawberry jam. Eat warm or cold.