1. Preheat oven to 475°. Grate frozen butter using large holes of a box grater. Toss together grated butter and flour in a medium bowl. Chill 10 minutes.
2. Make a well in center of mixture. Add buttermilk, and stir 15 times. Dough will be sticky.
3. 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.
4. Roll dough to 1/2-inch thickness. Cut with a 2 1/2-inch floured round cutter, reshaping scraps and flouring as needed.
5. Place dough rounds on a parchment paper-lined jelly-roll pan. Bake at 475° for 15 minutes or until lightly browned. Brush with melted butter.
For Pillowy Dinner Rolls: Cut in 1/2 cup cold shortening instead of cold butter. You'll get a soft biscuit that stays tender, even when cool. Plus, shortening has a neutral flavor that will complement anything on your dinner plate.
For Sweet Shortcakes: Add 2 Tbsp. sugar to the flour, and replace buttermilk with heavy cream. The sugar lends the biscuits a subtle sweetness, and the extra fat in heavy cream gives them a crumbly texture like shortbread. They're the perfect base for shortcake desserts.
For Crunchy-Bottomed Biscuits: Warm a cast-iron skillet in the oven, and spread a bit of butter in the skillet before adding the biscuits. The bottoms will end up crunchy and golden brown and provide a sturdy base that holds up to a smothering of sausage gravy.
For Pickle Biscuits: Why didn't we think of these sooner? Stir 4 Tbsp. drained dill pickle relish into buttermilk before adding to flour mixture. Split baked biscuits, and top with ham and mustard for the World's Best Ham Sandwich! We promise.