Spray enameled Dutch Oven Pot with Pam on the sides (butter will cover the bottom.
Preheat oven to 350 degrees
Place butter and diced onion into pot and stir in to start cooking the onion down.
Add the drained canned chicken and continue to stir.
Begin to cook the rice in the microwave per instructions. If you are using a boxed version, you should cook that before you begin the rest of the recipe so it will be timed right. Leftover rice can be used as well.
Microwave the steamable veggies for just a couple of minutes to thaw them, they don't need to be completely cooked.
Add the rice to chicken & onions and continue to stir. Then add the veggies.
Next add the Cream of Celery, Mayo and Sour Cream and blend well. If the dish seems a bit dry you can add an additional can of Cream of Celery, I didn't have this issue however.
Once it's mixed well, even it out on the top, sprinkle pepper and paprika on top.
Cover with a layer of shredded cheese.
Sprinkle sporadically shredded parmesan cheese.
Bake in the oven at 350 degrees for 30 minutes or until the cheese is bubbling.