Place a baking sheet in the oven at 200°C fan/gas 7. Add the flour, salt and baking powder into a food processor, then mix in the butter until well combined. Blitz in the sugar, add into a large bowl, then make a well in the middle of the ingredients.
Heat the yogurt, milk and vanilla together in the microwave for 1 min or in a pan; it should be hot and may look a little lumpy. Add to the bowl and quickly mix into the flour mix using a cutlery knife. As soon as the mixture has been fully added, stop.
Tip the dough onto a floured, then, with floured hands, fold the dough over a few times to create a smooth dough. Press out to about 4cm thick, dip a 7cm cutter into more flour, then stamp out 4 discs, adding flour to the cutter each time. flouring the cutter each time. Squash the remainder of the dough lightly together, then repeat until the dough has been used up. Brush tops with egg wash,sprinkle flour over the baking sheet and then transfer the scones to the tray. Bake for 12 minutes until golden and risen. Best enjoyed warm with jam and cream.