01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper or lightly grease it.
02 - In a large bowl, whisk together the whole wheat flour, all-purpose flour, baking soda, salt, and sugar until well combined.
03 - Stir in the currants until evenly distributed throughout the flour mixture.
04 - Make a well in the center of the dry ingredients. Pour in the buttermilk and melted butter. Mix gently with a wooden spoon or your hands until a soft, sticky dough forms. Do not overmix.
05 - Turn the dough onto a lightly floured surface and shape into a round loaf, approximately 7 inches in diameter.
06 - Transfer the loaf to the prepared baking sheet. Using a sharp knife, cut a deep X across the top about 1/2 inch deep to help the bread bake evenly.
07 - Bake for 35 to 40 minutes, or until the loaf is golden brown and sounds hollow when tapped on the bottom.
08 - Cool on a wire rack for at least 30 minutes before slicing to allow the crumb to set.