Preheat oven to 450°F. Place a 10.25-inch cast iron skillet into the oven to preheat.
Measure the self-rising flour into a large mixing bowl.
Using the coarse side of a hand grater, quickly grate 1 stick (½ cup) cold hard butter into the self-rising flour. Working quickly, use fingers to gently distribute the shredded butter into the self-rising flour.
Add the buttermilk, then stir until just combined.
Turn onto a lightly floured surface and, using floured fingers, quickly pat to approximately the size of an 8.5x11 sheet of paper, which will be about ½ to ¾ thick. Very lightly dust the surface of the dough with flour from your fingertips, then fold the sheet of dough into thirds, as when folding a business letter. Repeat the patting, dusting, and folding steps seven times, or fewer if you feel the dough begin to tighten–overworked dough makes for a tough biscuit! The final time, pat the dough to a rectangle slightly larger than the size of your skillet. Using a round biscuit cutter or a drinking glass, cut into about 7 round biscuits. Gather up the scraps to form the 8th biscuit by hand.
With a handle mitt, carefully remove the preheated skillet from the oven. Drop melted shortening into the preheated skillet, then return to oven for a couple of minutes, until it is melted. Place each biscuit into the skillet and, using a fork, immediately turn to coat both sides with shortening.
Place the hot skillet into the oven, and reduce the oven temperature to 425°F. Bake until tops of biscuits are golden brown, about 12-18 minutes.
Remove from oven. Brush tops with additional melted butter. Serve while hot! Kitchen Note: This recipe is easily doubled to be cooked in a 12-inch skillet, and yields around 12 biscuits.