Whisk together dry ingredients in a large bowl. Using your fingertips, work the softened butter into the flour mixture. (Rub the flour/butter mixture between your thump and forefingers.) In a separate small bowl, whisk the egg and then whisk in the buttermilk. Make a well in the flour, and add most of the buttermilk mixture (reserve 1/4-cup) and whisk together with your fingers to form a loose dough. (Stiffen your fingers and rotate your hand like a beater.) If dough will not come together, add some or all of the remaining buttermilk mixture in 1 tablespoon increments.
On a well floured work surface, turn out the dough. Sprinkle with flour and shape into a circle. Knead 3 or 4 times gently then flatten slightly with the tips of your fingers so that the dough is 7 inches in diameter and 1-1/4 inches high. Cut a cross on the top all the way to the sides, transfer to a baking sheet and bake for 15 minutes. Reduce heat to 400 degrees for another 20 minutes. Check bread. When it is done it will sound hollow when thumped on the bottom, be well browned, and an instant read thermometer will read about 185 degrees when inserted halfway into the bottom. Let sit 1/2-hour before slicing.
