Preheat the oven to 425°F.
Sift the flour, baking powder, baking soda, and salt into a mixing bowl. Cut the butter into the flour with a pastry blender or a fork, or rub between your fingers, until the mixture resembles coarse crumbs. Stir in the rosemary. Stir in the 1/2 cup buttermilk a few tablespoons at a time. Knead the dough in the bowl just until it holds together, adding additional buttermilk, a tablespoon at a time, if the dough is too dry. Take care not to overwork the dough, or the biscuits will be tough rather than light and airy.
On a lightly floured surface, pat the dough into a circle about 7 inches in diameter and 1/2 inch thick. Using a 1-inch round cookie cutter, cut out 12 biscuits. You can gather up the scraps to roll out more biscuits, but these won’t be quite as light.
Place the biscuits on a large baking sheet. Bake until golden on top and lightly browned on the bottom, about 12 minutes.
Yield: 12 biscuits