In a large skillet over medium heat, cook the breakfast sausage until browned, about 8-10 minutes. Break into small pieces as it cooks.

In a large mixing bowl, whisk together the eggs, milk, and sour cream until smooth. Season generously with salt and black pepper.

Grease a 9x13 baking dish and layer half of the hash browns, half of the cooked sausage, and half of the cheddar cheese. Repeat with the remaining ingredients.

Pour the egg mixture evenly over the layered ingredients and gently press down to ensure it seeps through.

Cover with aluminum foil and refrigerate overnight.

Preheat the oven to 350°F (175°C) and bake covered for 45 minutes, then remove the foil and bake for an additional 20-25 minutes until golden brown.

Let sit for 5 minutes before serving, and garnish with freshly chopped green onions.