Preheat the oven to 375 degrees. Line a baking sheet with parchment or waxed paper.
In a bowl combine the dry ingredients and blend thoroughly. Cream in the butter with your fingers or a fork, until the mixture resembles coarse crumbs. Add the buttermilk a little at a time and, using your hands or a fork, work it in just until it's thoroughly incorporated and you have a smooth ball of dough. Don't overwork or overhandle the dough.
On a lightly floured surface, roll out the dough with a rolling pin to a circle about 7 inches in diameter, 1/2-inch thick. Using a small round cookie cutter or the rim of a shot glass, press out twelve 1-inch rounds. If you like, you can reroll the leftover dough to make more, but the texture of these will be denser than the others.
Place the dough rounds on the baking sheet and bake until golden on top and brown on the bottom, for about 15 minutes. Serve warm.
Follow the recipe above but substitute 1/4 cup milk for the buttermilk and add 1 tablespoon chopped fresh rosemary.