Preheat and prep. Heat your oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish with nonstick spray or butter.
Soften and whisk the base. In a large bowl, whisk together the cream cheese, sour cream, cream of chicken soup, and mayonnaise until smooth and creamy.
Season the mixture. Stir in garlic powder, onion powder, paprika, black pepper, and salt.
Taste and adjust salt if needed—especially if your chicken is seasoned.
Add the cheeses. Fold in the shredded cheddar and Parmesan until evenly distributed.
Stir in the chicken. Mix in the cooked chicken until every piece is coated. If you’re using add-ins like rice, noodles, or veggies, fold them in now. The mixture should be thick but spreadable.
Spread in the dish. Transfer the mixture to your prepared baking dish and smooth the top with a spatula.
Make the crunchy topping. In a medium bowl, combine the crushed crackers with melted butter.
Stir until the crumbs look evenly moistened and clump slightly.
Top the casserole. Sprinkle the buttery crumbs evenly over the chicken layer. Don’t pack them down—light and even is best.
Bake. Place the dish on the center rack and bake for 25–35 minutes, or until the casserole is bubbling at the edges and the topping is golden brown.
Rest and garnish. Let it sit for 5–10 minutes to set up a bit. Sprinkle with chopped parsley or chives for a fresh finish.
Serve. Spoon into bowls or plate with a simple salad, roasted vegetables, or crusty bread.