Preheat oven to 350°F (175°C).
Cook elbow macaroni according to package instructions until al dente. Drain and set aside.
In a large mixing bowl, combine the drained canned chicken, cooked macaroni, frozen peas, frozen diced carrots, shredded cheddar cheese, condensed cream of chicken soup, sour cream, milk, garlic powder, onion powder, black pepper, and salt. Mix thoroughly until well combined.
Transfer the mixture into a 9×13 inch baking dish, spreading evenly.
In a small bowl, mix the crushed buttery crackers with melted butter until the crumbs are evenly coated.
Sprinkle the cracker topping evenly over the casserole.
Cover the baking dish tightly with aluminum foil.
To freeze: Place the covered casserole in the freezer for up to 3 months.
To bake from frozen: Preheat oven to 350°F (175°C). Remove foil and bake covered for 50 minutes, then uncover and bake an additional 10 minutes until the topping is golden and the casserole is heated through.
To bake from thawed: Thaw the casserole overnight in the refrigerator. Preheat oven to 350°F (175°C). Bake covered for 35 minutes, then uncover and bake an additional 10 minutes until golden and bubbly.
Let the casserole rest for 5 minutes before serving.