Preheat oven to 400f. Lightly grease baking sheet.
In a large bowl mix flour, sugar, baking powder and salt. Cut in butter. Rub until mixture resembles breadcrumbs. Add raisins.
Make a well in the center of the mixture. Add the egg and 1/4 cup of the milk. Mix in egg and milk by knocking sides of the dry mixture into the center. Continue doing this until all ingredients are combined, adding milk a little at a time as required.
Turn out dough onto a floured surface and knead briefly. Roll dough to 1/2 inch thick and cut with a biscuit cutter. Collect off-cuts, knead, roll out and cut again. Repeat this process until all the dough has been used.
Brush with beaten egg and sprinkle with decorating sugar if desired.
Bake in preheated oven for 15 minutes or until golden brown and well risen. Allow to cool on a wire rack. Serve as is, or split and spread with butter or jam and whipped cream.