Hash Brown Potato and Egg Bake

I made this last week for hubby to take to work for breakfast. There are 5 people in his branch and this entire pan was GONE in less than 2 hours! I guess it was good--I wouldn't know though--I didn't have any! :-)

1/2lb bacon chopped
1 medium onion chopped
30oz bag frozen hashbrown potatoes thawed and drained
2 cups shredded cheddar cheese
1/4c grated parmesan cheese
9 eggs1 1/4c milk8oz sour cream
1t salt
1/4t pepper
1t ground mustard
1/2-1c corn flakes
2Tbutter melted

Heat oven to 350. Spray 13x9" glass baking dish with cooking spray.In 10" skillet, cook bacon and onion over medium-high ehat about 10 minutes, stirring occasionally, until bacon is crisp and onion is tender; drain on paper towels.In large bowl, toss bacon mixture, potatoes, and cheeses. Spoon into baking dish. In same bowl, beat eggs, milk , sour cream, salt, and pepper and mustard with whisk until well mixed. Pour egg mixture over potatoe mixture.Bake uncovered 35 minutes.Meanwhile, in a small bowl, toss cornflake crumbs and butter, sprinkle cornflake mixture over partially baked casserole. Bake uncovered 10-15 minutes longer or until knife inserted in center comes out clean!