In a pan over medium heat, add the ground sausage. Break up the sausage as it cooks, and continue cooking until it is no longer pink.

Reduce the heat to low and add the butter to the pan. Whisk in the all-purpose flour and cook for about a minute, stirring constantly.

Gradually whisk in the milk, adding it about ½ cup at a time. Continue stirring until the gravy thickens and reaches your desired consistency.

Season the gravy with salt and pepper to taste.