Preheat your oven to 400°F (200°C). Grease a 9x13-inch baking dish with cooking spray or butter.
In a large skillet, heat olive oil over medium heat. Add the shredded chicken and frozen mixed vegetables. Stir in the chicken broth, 1 cup of milk, garlic powder, onion powder, thyme, salt, and black pepper. Cook for about 5-7 minutes until heated through.
Pour the chicken and vegetable mixture into the prepared baking dish, spreading it evenly.
In a mixing bowl, whisk together the flour, baking powder, and ½ teaspoon salt. Add the melted butter and ½ cup of milk, stirring until just combined. The batter will be thick.
Drop spoonfuls of the biscuit batter over the chicken mixture, covering it as evenly as possible.
Bake in the preheated oven for 25-30 minutes, or until the biscuit topping is golden brown and cooked through.
Remove from the oven and let it cool for a few minutes. Garnish with fresh parsley before serving.