Preheat oven to 400°F Lightly coat a baking sheet with cooking spray; set aside.
For the biscuits, in a medium bowl, gently stir together the 3 cups flour, the buttermilk, and butter until the dough just comes together. On a floured surface, pat the dough into a 1 1/2-inch-thick round. cut the dough into six 4-inch circles; transfer to the baking sheet. Bake about 25 mintues or until golden brown.
For the gravy, in a large skillet, cook the sausage over medium heat until brown, breaking meat up with a fork as it cooks. Using a slotted spoon, transfer sausage to a paper towel-lined plate to drain. Pour off all but 2 tablespoons fat from the skillet.
Heat the remaining fat over medium heat and whisk in the 4 1/2 tablespoons flour; cook and stir for 2 minutes. Slowly whisk in the milk; increase heat to medium-high and simmer about 3 minutes or until thickened. Stir in the sausage, pepper, and salt. To serve, split the biscuits and top with generous spoonfuls of gravy.