Preheat the oven to 350 degrees and spray a baking dish for your casserole.
Take a saucepan and add the water, 2 tbsp butter, and stuffing mix. Heat it until all ingredients mix.
Remove the pan from heat and cover it so the water is absorbed by the stuffing. Mix it at this time with a fork for better consistency.
Take a skillet now and add the remaining butter. Add the onion and celery, cook it for 5-7 minutes.
Add the sour cream, to the other cans and heat it on high flame until you have a smooth mixture.
Now on the baking pan, add the chicken and cover the bottom. Top it with the mixture you just prepared. Add salt and pepper to taste on the top of the mixture. Add the stuffing on the top and cook it in the preheated oven for 45-50 minutes.