For a different cheese flavor, replace some of the Parmesan with shredded cheddar, mozzarella, or another good melting cheese.
Bell peppers, mushrooms, chopped broccoli, or fresh herbs can also be added. Vegetables that release significant moisture are best cooked and drained before being mixed into the eggs.
For meal prep, divide the cooled casserole into individual portions and store them in airtight containers.