Grate frozen butter using large holes of a box grater.
Toss together grated butter and flour in a medium bowl. Chill 10 minutes.
Make a well in center of mixture. Add buttermilk, and stir 15 times. Dough will be sticky.
Turn dough out onto a lightly floured surface. Lightly sprinkle flour over top of dough. Using a lightly floured rolling pin, roll dough into a 3/4-inch-thick rectangle (about 9 x 5 inches). Fold dough in half so short ends meet. Repeat rolling and folding process 4 more times.
Roll dough to 1/2-inch thickness. Cut with a 2 1/2-inch floured round cutter, reshaping scraps and flouring as needed.
Place dough rounds in a cast-iron skillet or on a parchment paper-lined jelly-roll pan. Bake at 475° for 15 minutes or until lightly browned. Brush with melted butter.
If you want Crunchy-Bottomed Biscuits warm a cast-iron skillet in the oven and spread some butter in the skillet before adding the biscuits. The bottoms will end up crunchy and golden brown.