1. Preheat oven to 450°F (230°C).
2. For the biscuits, combine flour, baking powder, baking soda, and salt in a bowl. Cut in butter until the mixture resembles coarse crumbs. Gradually stir in buttermilk until dough forms.
3. Roll out the dough to 1-inch thickness and cut into rounds using a biscuit cutter. Place biscuits on a baking sheet and bake for 12-15 minutes, or until golden brown.
4. Meanwhile, prepare the gravy. In a skillet over medium heat, cook sausage until browned and crumbled. Do not drain the grease.
5. Sprinkle flour over the sausage and stir until combined. Slowly whisk in milk, cooking and stirring until the gravy thickens. Season with black pepper and salt.
6. Split the biscuits and pour the sausage gravy generously over them.