First things first, preheat the oven to 220°C (200°C fan oven, gas 7). Line a baking tray with greaseproof paper.
Sift the flour, Baking Powder, xanthan gum and sugar into a large mixing bowl and mix together. Add the butter and using your fingertips rub the butter into the flour mixture until it resembles breadcrumbs. Lift your hands while doing this to encourage air into the mixture.
Mix in the sultanas, then add the egg and Vanilla Extract and mix again. Gradually add the milk mixing after each addition; the dough will be quite sticky.
Turn the dough onto a lightly floured surface and lightly knead until all the dough comes together, avoid over handling the dough. Press the dough to flatten until it is around 2cm in thickness, cut the scones out using a 6cm diameter fluted round cutter. Gather any trimmings together, and flatten as necessary and cut out more rounds, you should get about 6-8 scones from the mixture.
Arrange the scones on the prepared baking tray. Mix the egg and milk to make the glaze and brush over the top of the scones. Place in the oven and bake for 12–15 minutes until risen and golden brown. Cool for a few minutes then transfer to a cooling rack.
