01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together all-purpose flour, whole wheat flour, sugar, baking soda, baking powder, and salt until well combined.
03 - Add cold butter cubes to the flour mixture. Using a pastry cutter or your fingertips, work the butter into the flour until the mixture resembles coarse crumbs with some pea-sized pieces remaining.
04 - Stir the dried currants into the flour-butter mixture until evenly distributed.
05 - In a separate bowl, whisk together cold buttermilk and egg until blended.
06 - Pour the buttermilk mixture over the dry ingredients. Stir gently with a fork until just combined; the dough should be shaggy and slightly sticky. Do not overmix.
07 - Turn the dough onto a lightly floured surface. Gently pat into a 1-inch thick circle. Cut into 8 wedges and transfer to the prepared baking sheet, spacing them evenly apart.
08 - If desired, sprinkle tops with demerara or turbinado sugar for added crunch and sweetness.
09 - Bake for 18 to 20 minutes until golden brown and a toothpick inserted into the center comes out clean.
10 - Let scones cool slightly on the baking sheet, then transfer to a wire rack. Serve warm or at room temperature with salted butter and jam.