Mix cream of chicken soup, sour cream, green onions, salt, pepper, onion, and garlic powder in a medium bowl. Include chicken and corn (or preferred vegetable). Transfer mixture to a greased 9x13 baking dish.
Mix melted butter with Ritz crackers in a small bowl. Evenly sprinkle this mixture on chicken. Bake casserole in preheated oven for 25-35 minutes until topping is golden and casserole bubbles.