1. Preheat oven to 400°. Combine first 3 ingredients in a large bowl; cut in butter with a pastry blender until mixture resembles coarse meal. Chill 10 minutes.
2. Add buttermilk to flour mixture, stirring just until moistened. Turn dough out onto a lightly floured surface; knead lightly 3 or 4 times.
3. With floured hands, pat dough into a 1/2-inch-thick rectangle (about 9 x 5 inches); dust top with flour. Fold dough over itself in 3 sections, starting with short end (as if folding a letter-size piece of paper). Repeat once, beginning with patting dough into a rectangle.
4. Pat dough to 3/4-inch thickness. Cut dough with a 2-inch round cutter, and place 1 inch apart on a parchment paper-lined baking sheet.
5. Bake at 400° for 13 to 15 minutes or until golden brown. Remove from baking sheets to wire racks; cool 2 minutes. Serve warm.