How to Make It
Preheat the oven to 450°. In a large bowl, whisk the flour with the baking powder, sugar, salt and baking soda. Using a pastry blender or 2 knives, cut in the shortening and the butter until the mixture resembles coarse meal. Make a well in the center and add the buttermilk. Using a wooden spoon, stir just until a dough forms. Turn the dough out onto a lightly floured surface and knead 3 or 4 times.
Pat or roll the dough out to a 1/2-inch-thick round. Using a lightly floured 2 1/2-inch round biscuit cutter, stamp out 24 biscuits as close together as possible. Transfer the biscuits to an ungreased baking sheet and bake for 15 to 20 minutes, or until the biscuits are risen and golden. Serve warm.