To make the biscuits: Preheat the oven to 450°F and line a baking sheet with parchment paper. Sift together the dry ingredients in a mixing bowl.
Cube the shortening or butter, then cut it into the dry ingredients. You can do this by hand with a pastry blender or with your food processor, Pulse until it becomes crumbly and resembles peas.
Stir in the cold buttermilk, just until the dough is thoroughly moistened. Sometimes I use ¾ cup and sometimes as much as 1 cup of buttermilk. The dough shouldn't be overly wet, but, slightly sticky.
Roll out on a lightly floured surface about ¾ inches thick and cut into rounds. Brush off an excess flour.
Brush the tops with melted butter or heavy cream and bake at 450°F for 13-15 minutes until lightly golden and puffy. Yield: 8  inch biscuits or 10  inch biscuits
To make the gravy: Place the sausage in a heavy bottomed pan or cast iron skillet. Cook over medium-high heat until no pink remains. Break the sausage up with a spoon as it cooks.
Cook until browned.
Drain all but 3 Tbsp of drippings from the pan. Sprinkle the all purpose flour over the sausage. Stir until the sausage is coated continuing to cook until lightly browned. Season with the salt and black pepper.
Over medium-high heat begin adding the milk, stirring constantly. Add 4 cups,adding more as needed to thin to your desired texture.
After all of the milk has been added, bring to a simmer. Lower the heat and cook for 5 minutes, stirring occasionally.
Serve immediately over hot biscuits with a sprinkle of black pepper.