Asparagus, Ham and Egg Bake

1 lb fresh asparagus spears, cut into 1-inch pieces

1 bag (30 oz) frozen shredded hash brown potatoes, thawed

1 medium onion, chopped (1/2 cup)

2 cups shredded Cheddar cheese (8 oz)

1/4 cup grated Parmesan cheese

12 eggs

1 1/4 cups milk

1 container (8 oz) sour cream

2 teaspoons lemon-pepper seasoning salt

2 teaspoons ground mustard

1 cup cornflake crumbs

2 tablespoons butter or margarine, melted