Pre-heat your oven to 220°c (200°c for fan assisted oven or Gas Mark 7). Grease two baking sheets with a little butter and set aside.
Sift the flour, salt, bicarbonate of soda and cream of tartar into a large bowl, holding the sift up to allow some air into them.
Gently stir in the sugar.
Using the tips of your fingers, rub in the butter to the dry ingredients, again lifting as you do to allow air in. Continue until you have a sandy consistency.
Stir in the sultanas and create a well in the middle.
Whisk the milk and sour cream together before pouring into the well. Using your hands, gently bring the ingredients together to form a soft, slightly sticky dough.
Turn out onto a floured work surface and gently knead together, before stretching the dough to about 2cm thickness.
Using a cookie cutter of your choice, cut your scones out and place them onto your pre-greased baking sheets. The smaller your cutter the more scones you will get. Reform and stretch the dough as required to use all of the dough.
Leave your scones to rest on the tray for about 10 minutes before brushing the tops with some beaten egg.
Bake in your pre-heated oven for 10 minutes. If you are making smaller scones, keep a close eye on them as you may need to reduce the baking time to suit.
Once cool enough to touch, transfer to a wire rack to cool completely or enjoy whilst still warm.
See our Top Tips above for more advice on getting the perfect scones.