Grease a 13×9 casserole dish. Cut 6 biscuits into cubes and layer in the bottom of the dish.
Cook sausage in a skillet until browned and fully cooked. Remove from skillet with a slotted spoon and spoon on top of the cut biscuits. Then drain all but 3 T. of the grease from the skillet. Whisk in flour and cook for 2 minutes. Slowly add 1 1/2 c. milk, bring to a boil and simmer until thickened to desired gravy consistency. Stir in 1/4 t. black pepper.
In a bowl, whisk together eggs and 2 c. milk. Season with salt and pepper to taste. Pour into casserole dish. Top with cheese. Refrigerate at least 30 minutes, or up to 10 hours before baking.
Bake at 350 degrees for 45-60 minutes, until fully cooked.