Preheat oven to 475°F. Prepare a parchment-lined sheet pan.
Sift flour into a bowl. Grate the frozen butter through the large holes of a box grater directly into the flour; toss briefly. Place bowl in the freezer while the oven preheats.
Make a well in the center and pour in the buttermilk. Stir until just combined — dough should be sticky and slightly wet. Turn out onto a well-floured surface and pat into a rectangle.
Fold the dough in thirds like a letter, then flatten. Rotate 90° and repeat. Do this 4 times total, handling as little as possible.
Roll or pat out and cut biscuits with a cutter or glass — do not twist. Arrange in a honeycomb pattern on parchment (touching sides help them rise). Brush tops with melted butter.
Bake 12–15 minutes until lightly browned. Transfer to a towel-lined basket and cover to keep moist.
