01 - Preheat the oven to 425°F. Line a baking sheet with parchment paper.
02 - In a large mixing bowl, whisk together the flour, baking soda, salt, and sugar until well blended.
03 - Create a well in the center of the dry ingredients and pour in most of the buttermilk. Mix gently with your hand or a wooden spoon until a soft, shaggy dough forms, adding additional buttermilk only if necessary to bring the dough together.
04 - Turn the dough onto a lightly floured surface. Knead briefly for about 30 seconds just to bring it together—avoid overworking. Shape into a round loaf approximately 2 inches thick and place on the prepared baking sheet.
05 - Using a sharp knife, cut a deep cross pattern on top of the loaf, cutting about halfway through the dough.
06 - Bake for 35 to 40 minutes until the loaf is golden brown and sounds hollow when tapped on the bottom.
07 - Transfer to a wire rack and cool for at least 10 minutes. Serve warm, cut into thick slices, with generous portions of Irish butter.