Breakfast Casserole with Mushroom Gravy Made with Cream of Mushroom Soup

Name: Breakfast Casserole with Mushroom Gravy (Made with Cream of Mushroom Soup)
Ingredients: 1 pound breakfast sausage; 4 cups shredded cheddar cheese; 8 slices of bread; 6 eggs; 2 cups milk + 1/2 cup milk, reserved; 1 can of Cream of Mushroom soup; 1/2 tablespoon dried Italian Herbs; 3/4 teaspoon dry mustard powder; 1/2 teaspoon salt; Freshly cracked black pepper