Preheat the oven to 375°F. In a large bowl, combine the first six ingredients. Cut in the butter with a pastry blender or work it in with your fingers. Mix the egg and buttermilk together, then add this mixture to the dry ingredients. Stir until well blended. Add the currants and stir the mixture well. Turn out onto a floured surface and knead gently for 3 minutes, or until the dough is smooth. Divide the dough into two pieces, shaping each into a round loaf. Place each into a greased 8-inch cake or pie pan, pressing it down until the dough fills the pan. Use a sharp knife to cut a ½-inch-deep cross on top of each loaf. Bake for about 40 minutes, or until the bread sounds hollow when you thump it. Turn out onto a wire rack to cool. Do not cut for about 4 hours.