The key to making these biscuits light and flaky is working the dough as little as possible. Shawn McClain adds Parmigiano-Reggiano to give them a great savory flavor. Slideshow: More Bread Recipes
Preheat the oven to 425°. In a large bowl, whisk together the flour, Parmigiano-Reggiano, chopped thyme, baking powder, salt, sugar and baking soda. Using a pastry cutter or 2 knives, cut in the chilled shortening and butter until the mixture resembles coarse meal. Add the buttermilk and mix gently until just incorporated.
On a floured work surface, using a rolling pin, gently roll out the dough to a 13-inch round, about 1/2 inch thick. With a 2 1/2-inch fluted biscuit cutter, cut out as many biscuits as possible. Transfer to 2 large baking sheets, leaving about 1 inch between biscuits. Gather the dough scraps, gently press them together and cut out 5 or 6 more biscuits.
Bake the biscuits for about 18 minutes, until they are golden brown and risen. Serve hot or warm.
The biscuits can be kept at room temperature for up to 3 hours; reheat before serving.