4 cups plain flour
1 tsp salt
1 tsp baking soda
1 tsp sugar (optional)
2 cups buttermilk or sour milk (hint: add 2 tsps vinegar to 2 cups plain milk)
Preheat oven to 440°F. Sieve the dry ingredients into a large bowl. Scoop up handfuls and allow to drop back in to aerate the mixture. Add enough buttermilk to make a soft dough. Now work quickly as the buttermilk and soda are already reacting. Knead the dough lightly - too much handling will toughen it, while too little means it won't rise properly.
Form a round ball as big as your fist. Place it on a lightly floured board and cut a cross in the top with a floured knife. Put near the top of the oven for 30 to 45 minutes. When baked the loaf will sound hollow when tapped on the bottom with your knuckles. Wrap immediately in a clean tea towel to stop the crust hardening too much.