Martha and chef Neil Kleinberg of the Clinton Street Baking Company prepare his signature recipe for perfect buttermilk biscuits.
In a large bowl, whisk together flour, salt, baking powder, and sugar; set aside. In the bowl of an electric mixer fitted with the paddle attachment, mix together shortening and butter. Add flour mixture to shortening mixture and mix together until crumbly. Add buttermilk and stir until just incorporated.
Sprinkle a rimmed baking sheet lightly with flour. Turn biscuit dough out onto a 13-by-9 1/2-inch rimmed baking sheet and gently press dough to cover. Using a rolling pin, roll surface of dough until evenly distributed. Cover dough with plastic wrap and transfer to a refrigerator to chill for at least 20 minutes, or until ready to bake, up to 1 day.
Preheat oven to 400 degrees. Line a baking sheet with parchment paper.
Cut biscuit dough using a 2 1/2-inch round biscuit cutter and transfer biscuits to prepared baking sheet, rerolling scraps one time, if necessary. Bake until golden, about 18 minutes. Serve immediately.