Preheat the oven to 475?F.
Sift the self-rising flour, cake flour, baking powder, baking soda, sugar, and salt into a large bowl. Using your fingers or a pastry cutter, work the 4 tablespoons cold butter into the flour until the pieces are pea size. Add the buttermilk to the flour mixture and, with your hands or a rubber spatula, stir just until the milk and flour come together to form a dough. Sprinkle some of the all-purpose flour on a work surface and place the dough on top of the flour. Using your hands, press the dough into a 1/2-inch-thick disk about 8 inches in diameter. Using a 3-inch round cutter dusted with flour, cut out dough rounds. Be sure to press straight down when cutting the dough-a twisting motion will prevent the dough from rising. You will need to re-form the scraps of dough to make 8 biscuits. Do this by pushing the scrap pieces together and pressing them into a 1/2-inch-thick disk.
Place the biscuits on a small sheet pan and brush the tops with the 2 tablespoons melted butter. Bake in the oven for 10 to 12 minutes, or until golden brown. Allow to cool briefly.
Makes eight 3-inch biscuits