Cheesy Broccoli-Cauliflower Casserole

Source: Joyce'S Fine Cooking

1 can cream of celery soup
1 cup mayonnaise
1 egg - beaten
1 large onion, chopped
2 packages frozen chopped broccoli (10 oz)
1 package frozen cauliflower (10 oz)
12 oz. shredded Cheddar cheese
1/2 tsp salt
1/4 tsp pepper

Topping
1/2 stick melted butter
3 tbsp of Parmesan or Asiago cheese (I use Asiago)
1 cup of bread crumbs

Spray a large casserole dish with non-stick spray. In a mixing bowl combine soup, mayonnaise, onion and beaten egg. Place partially thawed broccoli and cauliflower in another large mixing bowl. Stir in onion, soup, mayonnaise and egg mixture. Add 8 oz. cheese and seasonings and mix well. Pour mixture into prepared casserole dish.Toss together the Asiago cheese, bread crumbs & melted butter. Sprinkle evenly over top of casserole. Bake at 350º for 45 minute. Top with remaining 4 oz. of cheese and bake 5 minutes longer.