In a large bowl, whisk together the flour, sugar, baking soda and salt. Using a pastry cutter, cut the butter into the flour mixture until it resembles a coarse meal.

Whisk together the buttermilk and egg. Add to the flour mixture and stir until the dough comes together (the dough will be sticky). Turn the dough out onto a flour surface and knead with floured hands just until the dough comes together into a ball. Form into a ball about 7 inches in diameter.

Place the loaf in a cast iron skillet or on a baking sheet lined with parchment paper. Use a sharp knife to cut an X shape into the top of the loaf.

Bake for 45-50 minutes or until golden and the loaf sounds hollow when tapped.