Pre-heat the oven to 200ºC fan assisted.
Cut the butter into small pieces. Mix the flour with the salt, bicarbonate of soda and then mix/rub in the butter pieces. Now stir the egg into buttermilk and whisk until completely mixed in. Pour the buttermilk egg mixture into the flour mixture. Take a fork and roughly mix the dough together. Now wet your fingers with cold water and bring the dough quickly together with your hands. Finally dust your hands with flour and form the dough into a ball and place on a baking tray covered with baking parchment paper or cast iron skillet.
Score a deep cross in the top with a very sharp knife and place in the preheated oven.
Bake for 35min then turn the loaf upside down and bake for another 5min. Transfer to a wire rack and leave to cool for a few minutes.
Serve while still warm by either slicing it or breaking into quarters and then cut in half.