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 tblsp 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 cheddar cheese and bake 5 minutes longer.