Mom's Sausage Gravy

1 lb sausage, browned
8 Tbsp flour
1/2 stick butter
1/2 tsp salt
sprinkle of pepper
4 cups milk. 

Brown sausage. Add in flour and butter.  Mix till mixed in all the way.  Add salt and pepper.  Lastly, add in the milk.  Let heat and simmer, mixing frequently till thickened.