Sausage and Egg Breakfast Casserole

2 lbs frozen shredded hashbrowns
1 lb breakfast sausage, browned and drained
1/2 cup yellow onions, diced (or 6 green onions, chopped)
2 to 3 cups shredded cheese, mixture of cheddar and mozzarella preferred
12 large eggs
1/4 cup milk
1/4 teaspoon dry mustard
1/4 teaspoon garlic powder
1 teaspoon salt
1/2 teaspoon pepper
More salt and pepper to season the hasbrown layers, to taste

1. Lightly brease the insert to a large (6 quart) slow cooker with nonstick spray.
2. Layer 1/3 of the hashbrowns on the bottom, then lightly sprinkle with salt and pepper. 
3. top with 1/3 of the cooked sausage, then 1/3 of each the onions and cheese. 
4. Repeat layers two or more times, ending with the cheese.
5. In a medium bowl, whisk together the eggs and seasoning. Pour over the layers in the slow cooker. 
6. Cook on Low for 6 to 8 hours or High for 3-4 hours. (Edges may brown.)

Source: Seeded at the Table