Preheat Oven to 450 degrees F
In a large mixing bowl, sift 2 1/2 cups of flour, baking powder, sugar, stir and set aside
Roll stick of frozen butter into flour mixture and grate frozen butter using the large holes of the box grater. Toss together grated butter and flour. Chill in refrigerator for 20 minutes.
Make a well in the center of flour mixture. Add chilled buttermilk and stir with a spatula or wooden spoon for 10 times. dough should almost come together and be sticky.
Turn dough out onto floured surface. Lightly sprinkle flour over the top of the dough. Bring together with hands, then rolling pin. Roll dough into a 3/4 inch-thick rectangle (about 9x5 inches). Fold dough in thirds, like an envelop. Repeat rolling and folding process 5 more times. Use a bench scraper to prevent dough from sticking to surface and occasionally lightly sprinkle flour on board to keep it moving.
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 on a parchment paper lined baking sheet so that the rounds touch. Brush with melted butter. Bake at 450 for 15 minutes, or until lightly browned. Remove, Brush with remaining 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.