Heat the oven: Preheat the oven to 350°F and grease a 9x13-inch baking dish.
Beat the creamy base: In a large bowl, beat the softened cream cheese and sour cream together until smooth. Beat in the cream of chicken soup, garlic powder, onion powder, salt, and pepper.
Fold in chicken and cheese: Stir the cooked chicken and shredded cheddar into the creamy base until everything is coated.
Spread it out: Spread the chicken mixture into the prepared baking dish in an even layer.
Make the topping: In a small bowl, toss the crushed crackers with the melted butter until evenly coated, then scatter them over the top of the casserole.
Bake: Bake uncovered for 30-35 minutes, until the filling is hot and bubbling at the edges and the cracker topping is golden.
Rest and serve: Let it rest for 5 minutes, sprinkle with parsley, and serve.
Notes
Toss the crushed crackers with melted butter before topping the casserole so they bake up golden and crunchy. Uses fully cooked chicken; bake until the filling reaches 165°F and bubbles at the edges.