Preheat the oven to 375°F. Line a baking sheet or cast iron skillet with parchment paper.
Mix: Combine the flour, sugar, baking soda, baking powder, and salt in the bowl of stand mixer fitted with the paddle attachment. Add the butter and mix on low speed until the butter is mixed into the flour. Alternatively, the butter can be blended into the flour mixture by hand using a pastry cutter.
Combine: In a measuring cup, combine buttermilk with egg. With the mixer on low speed, slowly add the buttermilk mixture to the flour mixture and mix until just combined. If mixing by hand, use a wooden spoon or firm spatula to mix. Dough will be very dry.
Add currants: Sprinkle remaining 1 tablespoon of flour on top of currants. Shake to disperse the flour and evenly coat. Add the currants and caraway seed (if using) to the dough and fold in. Dough will be very dry, so you may need to use your hands. Try not to over mix.
Shape: Place the loaf on the prepared pan or skillet, shape into a circle, and cut an X that's about a half-inch deep into the top of the bread with a knife.
Coat soda bread: Combine melted butter and buttermilk and brush about a third of the mixture over the top of bread to coat. If buttermilk is cold, the melted butter might solidify and you will have to gently warm the mixture so that it can be spread.
Bake: Place soda bread in preheated oven and bake for 45-50 minutes, brushing the buttermilk butter mixture over the top every 15 minutes or so, until the bread is golden brown and a toothpick inserted into the center comes out clean. Transfer from baking dish to cooling rack.