Preheat your oven to 350°F (175°C). Grease a 9 by 13 inch baking dish with butter or nonstick spray.

Heat a large skillet over medium heat. Add the sausage and break it into small pieces as it cooks. Stir until browned and cooked through, about 6 to 8 minutes. Drain excess fat if there is a lot.

In a large bowl, combine the cooked sausage, thawed hashbrowns, softened cream cheese, milk, and half of the shredded cheddar. Stir until mostly combined; a few small cream cheese lumps are fine.

Spread the mixture evenly into the prepared baking dish, pressing gently to level.

In a separate bowl, whisk the eggs until blended and slightly frothy. Pour the eggs evenly over the hashbrown mixture.

Sprinkle the remaining cheddar over the top.

Bake in the preheated oven for 45 to 50 minutes, or until the eggs are set in the center and the top turns golden brown. A knife inserted in the center should come out mostly clean.

Let the casserole rest for 10 minutes before slicing into squares. Serve warm.