Mix together the dry ingredients. With two knives, a pastry blender, your fingertips, or a stand mixer, cut or rub the butter and shortening in until the mixture looks like breadcrumbs., Whisk the egg and milk together. Add them to the dry ingredients all at once, mixing quickly and gently for about 20 seconds until you have a soft dough., Dump the dough onto a lightly floured work surface. Knead it a couple of times to bring it together. With the help of a dough scraper, shape the dough into a 6" x 6" square, about 3/4" thick. Run a rolling pin over the top once to even it out. Wrap it in plastic wrap, and place it in the freezer for 1 hour., Preheat the oven to 400°F., Remove the dough from the freezer, unwrap it, and set it on a work surface. It'll be very stiff, but still soft enough to cut with a sharp knife, sharpened dough scraper or rolling cutter (pizza cutter). Cut the dough into nine 2" squares, and place the squares on a lightly greased or parchment-lined baking sheet., Bake the biscuits for 16 minutes, or until they're a light, golden brown. Remove them from the oven, and serve hot, warm or at room temperature., Store, well-wrapped, on the counter for 3 days. Freeze for up to 3 months.