Heat oven to 190C/fan 170C/gas 5. Mix the flours and baking powder in a mixing bowl with a pinch of salt, if you like. Add the butter and rub with your fingertips until mixture resembles fine breadcrumbs (or use a food processor). Stir in ½ of the cheese and make a well in the centre.
Whisk the remaining ingredients together and pour into the well. With a cutlery knife, bring the mixture together to make a soft, but not sticky dough. Add a little more milk if the dough is too dry.
Turn onto a floured surface, then roll out to about 2cm thick. Stamp out 4 scones using a round cutter, then gather the trimmings and repeat until all the dough has been used. Put on a baking sheet, brush with milk and scatter over remaining cheese. Bake for 10-12 mins until golden. Cool on a wire rack.