In a large bowl whisk together eggs, egg whites, cottage cheese, salt, and black pepper.
Pour the egg mixture into the prepared baking dish.
Sprinkle all the baby spinach evenly on top of the egg mixture.
Sprinkle all of the gruyere cheese on top of the spinach.
Bake in a 400 degree oven for 50 minutes until the eggs puff up and the casserole does not jiggle.
Notes
Leftovers can be kept in an airtight container in the refrigerator for a few days and reheated in the microwave.I wouldn't suggest freezing this recipe as the water content wouldn't thaw well and it would lose its flavor.Variations
As I mentioned above you can add in different proteins such as breakfast sausage, bacon, or ham.
Keep it vegetarian and use different types of veggies such as bell peppers, green onions, broccoli florets, tomatoes, or zucchini.
Add in your favorite fresh herbs and spices such as garlic, onions, basil, parsley, and red pepper flakes.
Use different types of cheeses such as Parmesan, mozzarella, swiss, or sharp cheddar cheese.
Nutritional information is provided as a courtesy and is an estimate only. This information comes from online calculators. Although attempts have been made to provide accurate nutritional information, these figures are only estimates.