Sift all the dry ingredients into a large bowl and mix well. Rub in the butter. Add the sultanas and gently mix together.
Lightly whisk the eggs and natural yoghurt together.
Make a well in the centre of the dry ingredients and add the egg and yoghurt mixture. Mix to soft dough, adding a little more natural yoghurt if necessary.
Turn onto a rice-floured board and knead lightly, just enough to shape into a round. Roll out to about 2.5cm/1in thick and cut out rounds using a 5.5cm/2¼in cutter. Place on a rice-floured baking sheet and brush with a little egg wash.
Bake for approximately 10 minutes until golden brown on top. Leave to cool on a wire rack.