Grease a 9×13 inch baking dish with cooking spray or butter.
Cook Sausage
In a large skillet, cook 1 lb of breakfast sausage over medium heat until browned and cooked through.
Break the sausage into crumbles as it cooks.
Remove from heat and drain any excess grease.
Prepare Layers
Spread 1 package (30 oz) of thawed hash browns evenly in the bottom of the prepared baking dish.
Top with the cooked sausage, ensuring an even layer.
Whisk Eggs and Milk
In a large mixing bowl, whisk together 8 large eggs, 1 cup of whole milk, salt, and pepper to taste until well combined.
Add Cream Cheese
Add 8 oz of softened cream cheese to the egg mixture and whisk until smooth and creamy.
Pour Over Layers
Pour the egg and cream cheese mixture evenly over the hash brown and sausage layers in the baking dish.
Add Cheese
Sprinkle 1 cup of shredded cheddar cheese and 1 cup of shredded mozzarella cheese over the top of the casserole.
Bake
Place the baking dish in the preheated oven and bake for 35-40 minutes, or until the casserole is set in the center and the cheese is melted and bubbly.
Garnish and Serve
Remove from the oven and let the casserole cool for a few minutes before serving.
Garnish with chopped green onions, if desired, and serve warm.
