Break sausage into small chunks and cook until well-browned. Remove sausage and reserve using a slotted spoon
Pour off all but 2 tablespoons of fat.
Whisk flour into the fat and continue to cook over low heat for 5 minutes, making a basic roux.
Remove pan from heat and whisk in milk a little at a time.
Return to medium-high heat and stir while the gravy comes to a simmer and thickens. (Be sure to scrape up any brown bits that might be stuck to the bottom of the pan, that's where the flavor is!)
Season with salt and pepper to taste. Add crumbled sausage and serve over buttermilk biscuits.
Notes
Traditionally, Sawmill gravy has a lot of cracked black pepper, usually coarsely ground. Do NOT use finely ground black pepper in this recipe.