Position an oven rack on the center rung and heat the oven to 450 degrees F. Lightly flour a small cutting board and set aside (this portable surface is easy to transfer to the refrigerator). Sift the flour, baking powder, salt, baking soda, and dried dill (if using) into a large, preferably shallow bowl. Mix in the fresh dill (if using) and the parsley. Add the shortening and butter to the dry ingredients. Combine with a pastry blender or two table knives just until a coarse meal forms. Make a well in the center and pour in the buttermilk. With your fingers (or a wooden spoon) and using just a few swift strokes, blend the dough just until combined (it will be a sticky mess; this is fine). Turn it out onto the floured cutting board. Wash, dry, and flour your hands. Gently pat out the dough and fold it back over itself about half a dozen times, just until smooth. Pat it out again, this time into a round or oval that's an even 1/2 to 3/4 inch thick. Cover the dough lightly with plastic wrap and refrigerate for about 20 min.

Remove the cutting board with the dough-from the refrigerator. Cut the dough with a sharp biscuit cutter--avoid twisting the cutter-- trying to get as many rounds as possible (the dough will toughen a bit each time you work it). Lightly pat the remaining dough scraps together, pat down evenly, and cut again. Position the biscuits at least 1/2 inch apart on a parchment-lined baking sheet. Bake, rotating the pan halfway through to ensure even cooking, until raised and golden brown (10 to 12 min. total for 3-inch biscuits; 9 to 11 min. for 2-inch biscuits).