Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the shredded chicken, sour cream, cream of mushroom soup, milk, garlic powder, black pepper, salt, and paprika. Mix until well combined.
Stir in the chopped green onions and half of the shredded cheddar cheese.
Transfer the mixture into a greased 9x13-inch baking dish.
In a separate bowl, mix the crushed crackers with the melted butter. Sprinkle the buttery cracker mixture evenly over the chicken mixture in the baking dish.
Top with the remaining shredded cheddar cheese.
Bake in the preheated oven for 30-35 minutes, or until the casserole is bubbly and the top is golden brown.
Let it cool for about 5 minutes before serving.