Preheat the oven to 400°F and line a baking sheet with parchment paper.

In a medium bowl, whisk together the buttermilk and egg.

In a large bowl, whisk together the flour, sugar, baking soda, and salt. Add the cubed butter and toss to coat. Use your hands to work the butter into the flour mixture until it is in roughly pea-sized pieces. Add the currants and stir to coat in the flour.

Make a well in the center of the dry ingredients and pour in the buttermilk mixture. Stir with a spatula or wooden spoon until a shaggy dough forms.

Turn the dough out onto a lightly floured surface and knead to form it into a ball. The dough should be soft but not too sticky. If it is very sticky, knead in a bit more flour. If it feels dry, add a bit more buttermilk.

Transfer the dough ball to the baking sheet and use a sharp knife to score the top with a ½-inch-deep cross. Bake for 45 to 50 minutes, or until the loaf is golden brown and it makes a hollow sound when you tap the bottom. If it is browning too quickly before it is cooked through, tent it with foil and continue to bake.

Remove from the oven and allow to cool for 10 minutes on the baking sheet before transferring to a wire rack to continue cooling.