Cut biscuits into quarters and line bottom of the greased pan.
Brown the sausage in a skillet and drain off any grease. Then layer over the biscuits in the pan.
Next, layer shredded cheddar cheese over sausage in the pan.
In a bowl whisk together eggs and ¾ c. milk until combined. Pour egg mixture over the biscuits. Cover and place in the refrigerator until the morning.
Next, mix up the gravy. In a saucepan melt 5 Tablespoons butter. Then whisk in 5 Tablespoons flour until paste-like. Add salt and pepper and whisk until combined.
With heat on medium high, gradually whisk in 1 1/2 c. of milk and stirring constantly. Bring to a boil, reduce heat to low and simmer 2-3 minutes until thickened.
In the morning, warm gravy until consistency is pourable. Pour over egg casserole.
Place covered casserole in preheated oven at 350 degrees Fahrenheit and bake for 35 minutes. Remove aluminum foil, place back in oven and bake an additional 25-30 minutes or until casserole is set in the middle, cheese is melted and it is golden brown on edges.