Prepare the Biscuit Dough : In a mixing bowl, combine the flour, baking powder, baking soda, and salt. Add the cold, cubed butter and cut it into the dry ingredients using a pastry cutter or your fingers until it resembles coarse crumbs. Pour in the buttermilk, stirring gently until the dough comes together. Be careful not to overmix. Transfer the dough onto a floured surface and carefully shape it into a rectangle, aiming for a thickness of about 1 inch. Cut the dough into rounds or squares for the top of the pie.

Cook the Sausage Gravy : In a large skillet over medium heat, brown the sausage, breaking it up with a spatula as it cooks. After the sausage is fully cooked, take it out of the skillet and set it aside, keeping the drippings in the pan. Add the butter to the skillet along with the drippings, then sprinkle in the flour, stirring continuously to create a roux. Allow the roux to cook for 1 to 2 minutes until it achieves a light golden color. Gradually whisk in the milk, mixing constantly to avoid any lumps. Bring the gravy to a gentle simmer, allowing it to thicken for approximately 3 to 5 minutes. Stir the cooked sausage back into the gravy and season with salt and freshly cracked black pepper to your liking. Finally, remove from heat.

Assemble the Pie : Preheat your oven to 400°F (200°C). Pour the sausage gravy into a lightly greased pie dish or casserole dish. Arrange the biscuit rounds or squares over the top, leaving a bit of space between each piece for even baking.

Bake : Place the assembled pie in the oven and bake for 20-25 minutes, or until the biscuits are golden and cooked through.

Serve : Allow the pie to cool slightly before serving. Scoop out generous portions and enjoy this hearty, comforting dish with a sprinkle of fresh herbs if desired.