Preheat your oven to 375°F (190°C) and lightly grease a 9x13-inch baking dish with butter or nonstick cooking spray.
In a medium mixing bowl, combine the condensed cream of chicken soup, sour cream, water, black pepper, and dried thyme, whisking until you achieve a smooth, uniform sauce.
Spread the frozen vegetables evenly across the bottom of the prepared baking dish, then arrange the raw chicken pieces in a single layer over the vegetables.
Pour the prepared sauce mixture evenly over the chicken and vegetables, ensuring everything is well coated.
Sprinkle the dry stuffing mix evenly over the top of the casserole, then drizzle the melted butter over the entire surface of the stuffing layer.
Bake uncovered for 35-40 minutes, until the chicken is cooked through, the sauce is bubbly around the edges, and the stuffing topping is golden brown and crisp.