Cut butter into dry ingredients. You can mash with a fork or use your fingers, but pastry cutter is best. (Get a real one! With blades, not wires.) Stir buttermilk into mix to form a soft dough. Turn out onto floured counter (or large cutting board), knead together briefly.
Rolling pin, biscuit cutter, pastry brush:
Roll dough (gently!) for evenness. Not too thin, about a half-inch high. Cut dough with large round cutter, straight down (do not twist!). Brush the tops with buttermilk (or egg or melted butter).
Bake in cast-iron frying pan at 450°F for 20 minutes.