2) Combine the 600g of flour and 25g of the sugar with the baking powder and salt in an electric mixer fitted with a paddle attachment. Blend in the cold butter at the lowest speed and mix until the butter is in pea-sized pieces.
3) Combine the eggs and double cream and quickly add to the flour/butter mixture. Combine until just blended.
4) Combine the sultanas with 1 tbsp of flour and then add to the dough and mix quickly. The dough may be a bit sticky.
5) Dump the dough out onto a floured surface and be sure it is well combined. Flour your hands and a rolling pin and roll the dough out to 1.5 to 2.5cm thick. You will see lumps of butter in the dough.
6) Cut squares with a 7cm cutter and then cut these in half diagonally to make triangles. Place the scones on the prepared baking tray.
7) Brush the scones with the egg wash and sprinkle with sugar. Bake for 20 to 25 minutes until the outsides are crisp and the insides are done.