In a mixing bowl, combine dry ingredients together with a fork. Cut in the shortening using a pastry blender until mixture resembles coarse crumbs. Make a well in the center and add buttermilk. Quickly fold dry ingredients into buttermilk with your hands until a sticky dough forms.
Turn dough out onto floured surface. Gently fold the dough over itself 3 or 4 times to create layers. Roll dough out to 3/4-inch thick. Cut with a 3-inch biscuit cutter. Transfer dough rounds to a sheet pan. Gather scraps and repeat. Make a dimple in the center to help the top rise evenly. Brush with butter. Bake for 15 minutes in a preheated 400 degree oven until golden brown.