Preheat your oven to 350º F and lightly grease your cast iron pan or Dutch oven with unsalted butter.
Sift together flour, baking powder, baking soda, salt, and sugar in a medium bowl.
Grate your cold butter into the dry ingredients.
In a separate bowl, whisk together eggs and buttermilk.
Add the buttermilk mixture to the dry ingredients and mix with a spoon (or your hand) until the dry ingredients are moistened.
Sprinkle in the caraway seeds and currants (or raisins) and fold in gently to combine.
Place the dough on your workbench, fold it over 7 to 8 times, and shape it into a ball. Do not overwork the dough or it will be tough.
Dust the surface generously with flour and use a sharp knife to cut a cross on top to allow the dough to spread and rise evenly.
Place the dough into the cast iron pan.
Bake for 1 hour, until the top is golden brown or the internal temperature reads 190º to 200º F.
Brush the warm loaf with the melted butter as soon as it comes out of the oven.
Video
Notes
Ingredient notes: Use a kitchen scale to weigh your ingredients, including liquids, unless otherwise instructed (Tablespoons, teaspoons, pinch, etc). Scaled ingredients are much more accurate than volume measurements and help ensure the recipe turns out right. Metric measurements are available by clicking "Metric" under the ingredients above.Buttermilk Substitute: Stir 2 Tablespoons of white vinegar into 8 ounces of regular milk and rest for 5 minutes. Pan options: No cast iron? Use a parchment-lined round cake pan or baking sheet, and reduce the bake time slightly, checking at 45 to 50 minutes. Stick close to a 10-inch pan, a wider one will spread the dough thinner than shown in the photos.Make-ahead and storage:Room temperature, tightly wrapped, 2 to 4 days. Refrigerator, 1 week. Freezer, up to 3 months. Slice before freezing for convenience. Warm slices in the microwave 15 to 30 seconds before serving.Substitutions: Currants or raisins can be swapped for dried cranberries, golden raisins, or chopped dried apricots. Skip the caraway seeds entirely if you're not a fan, or swap in fennel seeds. Optional: soak the currants or raisins in warm water or orange juice for 15 to 20 minutes before adding, then drain and pat dry, for plumper fruit in every bite.Critical do-nots: Don't overmix once the buttermilk mixture goes in, the dough should look shaggy, not smooth. Don't skip weighing your buttermilk if you can, measuring by volume is the most common reason the dough turns out too wet. Don't pull the loaf early, a pale crust usually means the inside isn't done yet.