Combine all of your ingredients in a large bowl, reserving half of the cheddar cheese and half of the onions for the topping later. Stir well to combine.
2 cups small shell pasta, 3 cups frozen mixed vegetables, 2 cups shredded cheddar cheese, 2 cups French fried onions, 2 cups shredded cooked chicken, 1 can cream of chicken soup, ¼ cup milk, 1 teaspoon pepper, 1 teaspoon garlic powder, ½ teaspoon salt
Spoon the casserole mixture into a 9x13 casserole dish. Bake for 25-30 minutes. Top with the remaining onions and cheese and return the casserole to the oven until the cheese has melted, about five minutes more.
2 cups shredded cheddar cheese, 2 cups French fried onions