Heat the oven to 375°F. Lightly grease a 9 × 13-inch baking dish.
In a large bowl, stir together the cooked chicken, cream of chicken soup, sour cream, ½ cup broth, frozen vegetables, garlic powder, onion powder, thyme, and pepper.
Spread the chicken mixture evenly in the baking dish.
In a separate bowl, stir the dry stuffing mix with 1½ cups broth and the melted butter until evenly moistened. Spoon it loosely over the chicken filling.
Bake uncovered for 30 to 35 minutes, until the filling bubbles around the edges and the stuffing is golden. Rest for 5 minutes before serving.
Notes
For the version I made, replace the boxed stuffing topping and its broth and butter with about 2 1/2 cups of preparedGrandma’s old-fashioned stuffing. Spoon it over the filling in a loose layer.