Heat oven to 425°F. Line a baking sheet or cast iron pan with parchment.
In a bowl mix the whole wheat flour, all purpose flour, baking soda, and salt.
Make a well in the center. Pour in most of the buttermilk.
Mix with your hand until it just comes together. Add the remaining buttermilk if it feels dry. The dough should be soft but not sticky.
Turn onto a lightly floured surface and gently shape into a round loaf about 2 inches thick. Do not knead.
Place on the baking sheet or cast iron pan and cut a deep cross on top with a knife.
Bake 35 to 40 minutes until the crust is firm and the bottom sounds hollow when tapped.
Let cool at least 20 minutes before slicing.
Serve thick slices with salted Irish butter. Perfect with smoked salmon, soup, or jam.
