Melt 1 tablespoon of the butter in a large frying pan over medium heat. Once melted, add the fresh homemade or frozen hashed browns to the pan. Cover and let steam for 4 minutes. Uncover, stir, and let them cook for 5 minutes before stirring again. Stir again and let cool for 5 more minutes, or until the potatoes start to brown and are cooked through. Transfer the cooked hashed browns to a 9 x 13" glass casserole dish. Using a spatula, spread the potatoes out into one even layer.

Melt the remaining butter in the frying pan and return to medium heat. Once melted, add the frozen spinach and cover. Let the spinach steam for about 4 minutes then uncover, stir, and continue to stir until it's completely melted.

In a large bowl, whisk the eggs together. Pour the cooked spinach into the eggs and whisk to combine. Pour the egg mixture over the hashed browns in the casserole dish and season with the salt.

Bake at 350 F for 35 minutes, or until the center of the dish is firm when shaken.

Let cool for at least 10 minutes and then slice and serve. Add additional salt and pepper to taste.

Note: the casserole is less likely to stick the longer you let it cool.