Pre-heat the oven to 170°C and line a large baking tray with baking parchment.
Tip the flours and starches into a large mixing bowl and whisk together well. Add the butter then rub together with your fingertips until the mixture resembles breadcrumbs.
Stir in the white pepper, mustard powder and baking powder.
Grate the cheese into the bowl and gently stir into the other ingredients.
Pour in the beaten eggs and turn into the mixture with a wooden spoon until completely incorporated.
Finally stir in the olives.
Once the olives are evenly dispersed carefully pour in the buttermilk, bringing the dough together with a wooden spoon.
Tip the dough onto a floured surface (you can use any flour, but not too much) and pat the mixture together, gently folding and turning the dough until the flour is incorporated.
Once the dough is dry enough to work with then using the palm of your hands flatten out to 1 inch thickness.
Cut the scones out of the dough using a 68mm round pastry/biscuit cutter with fluted edges.
Place the scones on the baking trays, then brush the tops with a little beaten egg mixed with a splash of buttermilk. Be careful not to let the egg wash drip over the sides of the scones or they will not rise evenly.
Bake the scones in the oven for 12-15 minutes until risen and golden.
Serve with plenty of whipped butter.
The scones are at their best warm from the oven. They don’t really last longer than a day before getting a little stale.
If you are not gluten-free then just substitute the sweet rice flour, oat flour, millet flour, potato starch and tapioca starch for 400g plain wheat flour.
If you don’t have buttermilk to hand you can use whole milk. Using the buttermilk though gives the scones a lovely soft crumb and a bit of a tangy note which pairs nicely with the salty olives and cheese.