Preheat your oven to 350°F (175°C). Grease a 9×13-inch casserole dish with cooking spray or butter.

In a large skillet over medium heat, cook the breakfast sausage, breaking it apart as it cooks until browned and crumbled. Once cooked through, drain any excess fat and set aside.

In a large mixing bowl, whisk together the eggs, milk, softened cream cheese, salt, and pepper until smooth and well-combined. The cream cheese should be fully incorporated into the egg mixture.

In the prepared casserole dish, spread the thawed hashbrowns evenly across the bottom. Layer the cooked sausage on top of the hashbrowns.

Pour the creamy egg and cream cheese mixture evenly over the sausage and hashbrowns, ensuring it spreads out uniformly.

Sprinkle shredded cheddar cheese generously over the top of the casserole.

Bake in the preheated oven for 45-50 minutes, or until the casserole is set and the top is golden and bubbly. To check for doneness, insert a knife into the center; if it comes out clean, the casserole is ready.

Remove from the oven and let the casserole rest for 5-10 minutes before slicing. Garnish with chopped green onions or parsley if desired, and serve warm.