Rub in the butter by hand or with a pastry blender until the mixture is mealy. Sprinkle the work surface generously with flour and scrape the dough onto it. Fold the dough over on itself two or three times. Use the dough immediately . Transfer to a parchment-lined cookie sheet.
Paint tops with buttermilk.
Bake for 10 to 15 minutes, until well risen and golden.