1. Preheat oven to 350 degrees F.
2. In a medium large bowl take mayonnaise, cream cheese, heavy cream, onion and beaten egg. Whisk well and keep aside.
3. In another large bowl take broccoli and cheddar cheese.
4. Pour mayonnaise mixture over the broccoli mixture.
5. Season with salt, pepper and paprika.
6. Pour the mixture in a baking dish, bake for 40 minutes at 350 degrees F.
7. Cut broccoli cheddar casserole into squares and serve.