Preheat oven to 375 degrees. Place a 10" UNGREASED cast iron skillet in oven to heat. In a large mixing bowl, combine the flour, sugar, baking soda, baking powder and salt. Cut in the butter or margarine with a pastry blender. Stir in the caraway seeds and currants. Stir in just until combined 1/2 cup buttermilk and the egg. Turn dough out on a floured cutting board. The dough will be sticky. With floured hands knead the dough a few times until able to form into a disc shape. Carefully remove the hot cast iron skillet from oven and lightly grease with butter. Place the round ball of dough into the skillet. In desired, cut an "X" into the top of the loaf using a toothpick. Brush the top of loaf with the remaining buttermilk. Bake for 35-40 minutes until golden brown and hollow when tapped. Serve warm.