Potato Casserole

My mom started making this potato casserole years  ago and it has become a family favorite.

1- Bag Frozen Hash brown Potatoes, cubed
1- Small Onion, finely diced
1- Can Cream of Celery Soup
1- LB Shredded Cheddar
1- LB Shredded Coby Jack Cheese
1- Stick of Butter, melted and divided
1- Cup Cornflakes, crushed
Salt n pepper to taste

In a large bowl combined the first 5 ingredients. Add 1/2 of the melted butter, mix well . Pour mixture into a casserole dish , top with cornflakes and remaining butter. Bake at 350 for 30-40 minutes , until cheese is melted and topping is golden brown.