1. Preheat oven to 400 degrees F. Coat a pie pan with cooking spray.
2. Whisk whole-wheat flour, all-purpose flour, sugar, baking soda, and salt in a large bowl. Stir in currants and caraway seeds.
3. Make a well in the center of the dry ingredients. Gradually pour in the buttermilk, stirring with a fork until just combined.
4. Turn the dough out onto a lightly floured surface and pat into a ball. Flatten slightly and place in the prepared pie pan. Brush the top with buttermilk and dust with flour. With a sharp knife, cut an X into the top of the loaf.
5. Bake the loaf until it is brown on top and sounds hollow when tapped on the bottom (30-40 minutes). Let cool for 2 hours before slicing.