Sift the flour, the optional sugar, baking soda, and salt into a bowl. Rub in the butter until the mixture resembles course meal. Stir in the buttermilk all at once and mix with a sppon until all ingredients are moistened. Turn out onto a lightly floured surface and knead 4 or 5 times. Roll or pat the dough to inch thick and cut rounds with a 2 inch cutter, or diamonds approximately the same size, reforming and recutting the scraps. Arrange the scones 2 inches apart on an ungreased baking sheet. Bakethe scones in the middle of a preheated 400F oven for 13 to 16 minutes, or until they are well risen and the tops are golden brown. Let the scones cool slightly on a rack, but serve them warm.