In a large saucepan over medium-high heat, brown sausage. Crumble the sausage the best you can so that you have small bits.
Add bacon grease to total about 1/4 cup cooking fat.
Add flour, stir and cook over medium heat for about three minutes.
Slowly add, while whisking, the 2 cups milk. Continue to cook for about five more minutes or until thickened to desired consistency.
You can add more milk to thin. If you want it thicker, add a teaspoon of cornstarch to a little bit of cold milk, stir well, and then add to the gravy.
Serve over warm biscuits.