Preheat the oven to 350 degrees. In a large cast iron skillet, melt the butter over medium heat. Add the zucchini, carrots, onion and celery. Cook and stir until the vegetables begin to soften. About 5- 7 minutes.

Sprinkle the flour over the vegetables and stir until it's dissolved. The flour and veggies will all clump together and this is normal. Slowly add the broth and milk to the mixture, stirring constantly. Cook and stir, making sure to scrape the bottom of the pan until the mixture is thick and bubbly.

Stir the chicken, sour cream and stuffing mix into the vegetables and sauce and season with salt and pepper. If you don't have a cast iron skillet, transfer the mixture to a greased 9x13 pan, otherwise place the cast iron skillet in the oven and bake uncovered for 40 minutes or until the top is golden brown.