Preheat your oven to 350°F and spray a 9×13-inch baking dish with nonstick cooking spray.
Spread half of the cut biscuit pieces in an even layer across the bottom of the dish.Bake in the preheated oven for 15 minutes, or until golden brown. Remove from the oven and set aside.
While the biscuits are baking, brown the pork sausage in a large skillet over medium heat. Once fully cooked, transfer the sausage to a paper towel-lined plate to drain while you prepare the country gravy.
In the same skillet with the sausage drippings, add the butter and stir over medium heat until melted.Sprinkle in the flour, stirring well to combine. Cook, stirring constantly, until the mixture begins to bubble.
Once the flour mixture starts bubbling and thickens slightly, pour in the milk and whisk until fully combined. Reduce the heat to low and simmer, stirring occasionally, until the gravy thickens to your desired consistency.
Once the gravy has thickened, remove the skillet from the heat and stir in the cooked sausage.
Pour the sausage gravy mixture evenly over the baked biscuits, ensuring they are completely covered.
Layer the remaining biscuit pieces over the top of the sausage gravy, then return the dish to the oven.
Bake the casserole at 350°F for 15–20 minutes, or until the top biscuits are golden brown.Remove from the oven.
Serve warm straight from the oven