Pre-heat the oven to 350°F.
Bring a small pot or kettle of water to a boil. Place the currants into a small bowl and cover with boiling water to reconstitute. Let stand until softened and plump, then drain. If using whisky, soak the currants in whisky for about an hour. Drain and reserve.
In a large mixing bowl, combine the flour, sugar, baking powder, salt and baking soda. Add the butter; use your hands to incorporate it into the flour mixture into large-sized crumbs. Mix in reconstituted the currants, caraway seeds and orange zest.
In a medium size mixing bowl, whisk together the buttermilk and eggs, and add to dry mixture. Using a wooden spoon, stir the dough until incorporated, making sure not to over-mix.
Grease the inside of a 12-inch cast iron skillet with butter. Place the dough into the skillet and smooth out the top. Cut a deep X into the top of the dough.
Bake the bread until deeply golden on top and a toothpick inserted in the center comes out clean, about 1 hour and 10 minutes. Leave bread in the skillet to cool for 15 minutes. Carefully remove the bread from the skillet and allow to cool completely.