Breakfast Casserole

6 eggs, beaten
1 pound of little smokies or 1 1/2 pounds of bulk sausage, browned and drained
1 1/2 cups of milk
1 cup of shredded cheddar cheese
8 slices of bread, torn into pieces
1 teaspoon of salt
1/2 teaspoon of dry mustard
1 cup of shredded mozzarella cheese