Preheat the oven to 425 F. Set a large baking sheet into the oven to heat up while the oven preheats.
In a food processor add the flour, salt, baking powder, and sugar. Pulse a few times to combine.
Add the cubed butter and pulse until the butter is integrated and the mixture resembles coarse sand. Transfer the mixture to a large bowl.
In a small bowl whisk together the milk and egg until well combined. Transfer 2 tablespoons of the mixture to a smaller bowl to save for later as an egg wash. Pour the rest of the mixture into the bowl with the flour mixture.
Gently mix the flour and egg mixtures together until a shaggy dough forms. Transfer the dough to a lightly floured surface and knead a few times with floured hands until the dough is smooth. Press the dough into a circle about 1 inch thick. Use a 2½-inch round cutter or floured glass to cut out scones. Take the cut-out scones and place them on a piece of parchment paper making sure they are touching. Use the dough scraps to create another circle to cut out more scones, repeating until all the dough is used.
Brush the tops of the cut-out scones on the parchment paper with the reserved egg wash. Carefully remove the hot baking pan from the oven and place the parchment paper on the hot baking sheet. Carefully place the baking sheet back in the oven and bake in the preheated oven for 13 to 15 minutes until golden.
Let scones cool, then serve with clotted cream or jam as desired.