Yes, you can use mashed potatoes instead of hash browns in breakfast casseroles, but expect a softer, denser texture rather than crisp potato pieces.
Essential Concepts
Use firm mashed potatoes as a base, reduce the milk in the eggs, and precook watery vegetables.
Related posts:
https://www.simplyrecipes.com/recipes/perfect_mashed_potatoes/
https://www.simplyrecipes.com/recipes/crispy_hash_browns/
