Preheat the oven to 375°F (190°C). Grease a 9x13-inch baking dish.
In a large bowl, combine cream of chicken soup, chicken broth, and sour cream until smooth.
Layer the cooked chicken evenly across the baking dish.
Spread the mixed vegetables (if using) over the chicken.
Pour the soup mixture evenly over the chicken and vegetables.
Prepare the stuffing mix according to package directions and spread it on top.
Bake for 25-30 minutes or until the top is golden and bubbly.
Let the casserole rest for 5 minutes before serving.