Preheat the oven to 400°F (200°C).
Pour the melted butter into a 9x13-inch baking dish, coating the bottom evenly.
Layer the shredded chicken and frozen vegetables over the butter. Do not stir.
In a mixing bowl, whisk together the biscuit mix, the included seasoning packet, and the milk until fully incorporated. Pour this mixture over the chicken and vegetables. Do not stir.
In another bowl, whisk together the cream of chicken soup, chicken broth, garlic powder, and black pepper. Slowly pour this mixture over the biscuit layer. Do not stir.
Place the dish in the oven and bake for 45 to 50 minutes, or until the biscuit topping is golden brown and the edges are bubbling.
Remove from the oven and let rest for 10 to 15 minutes to allow the sauce to thicken before serving.