01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - Whisk together all-purpose flour, whole wheat flour, sugar, baking soda, baking powder, and salt in a large bowl.
03 - Add cold butter cubes to flour mixture. Using pastry cutter or fingertips, work butter into flour until mixture resembles coarse crumbs.
04 - Stir dried currants into flour-butter mixture until evenly distributed.
05 - Whisk buttermilk and egg together in separate bowl until combined.
06 - Pour wet mixture over dry ingredients. Stir gently with fork until just combined. Do not overmix.
07 - Turn dough onto lightly floured surface. Pat into 1-inch thick circle. Cut into 8 wedges and place on prepared baking sheet.
08 - Optionally sprinkle tops with demerara or turbinado sugar for added crunch.
09 - Bake for 18-20 minutes until golden brown and toothpick inserted into center comes out clean.
10 - Cool slightly on wire rack. Serve warm or at room temperature.