In a large mixing bowl, combine the cooked and shredded chicken and chopped cauliflower florets.
In another mixing bowl, whisk together the sour cream, mayonnaise, grated Parmesan cheese, shredded cheddar cheese, minced garlic, chopped fresh parsley, and salt and pepper to taste.
Pour the mixture over the chicken and cauliflower mixture and stir until everything is evenly coated.
Transfer the mixture to a greased 9×13 inch casserole dish.
Bake the casserole in the preheated oven for 25-30 minutes, or until the top is golden brown and the casserole is heated through.
Remove the casserole from the oven and let it cool for a few minutes before serving.