- Heat the oven to 450°F (230°C) and line a baking sheet with parchment.
- Whisk the flour, baking powder, baking soda, salt and sugar. Cut in the cold butter with a pastry cutter or your fingertips until the pieces are the size of peas.
- Stir in the buttermilk just until a shaggy dough forms. Turn it onto a floured counter, pat into a rectangle and fold it over on itself 3 or 4 times to build layers.
- Pat the dough 1 inch thick and cut 2½-inch rounds, pressing straight down without twisting. Set them on the sheet with sides touching.
- Bake until tall and golden, 12 to 15 minutes.
- Meanwhile, brown the sausage in a large skillet over medium heat, breaking it up, 8 to 10 minutes. Do not drain the fat.
- Sprinkle the flour over the sausage and stir for 1 to 2 minutes. Slowly pour in the milk while stirring and simmer until thick enough to coat a spoon, 5 to 8 minutes.
- Season with the pepper and salt. Split the warm biscuits and ladle the gravy over them.