01 - Preheat oven to 425°F. Line baking sheet with parchment paper.
02 - Whisk flour, baking soda, salt, and sugar in large mixing bowl until well blended.
03 - Create well in center of flour mixture. Pour in most buttermilk. Mix gently with hand or wooden spoon until soft dough forms, adding remaining buttermilk if needed.
04 - Turn dough onto lightly floured surface. Knead briefly about 30 seconds until just combined. Shape into round loaf approximately 2 inches thick. Place on prepared baking sheet.
05 - Cut deep cross pattern on top of loaf with sharp knife. Bake 35-40 minutes until golden brown and bottom sounds hollow when tapped.
06 - Cool on wire rack for 10 minutes minimum. Serve warm, thickly sliced with generous Irish butter.