Preheat oven to 375 degrees. Heat an oven safe cast iron skillet over medium heat. Melt the butter and sauce the onion, sage and thyme until softened and fragrant (5-7 minutes). Add the garlic and cook for another 1-2 minutes. Season with salt and pepper. Coat the mixture with flour and continue stirring for 3-4 minutes to make a roux.
Whisk in the milk and broth. Increase heat and bring to a boil. Reduce to low-medium heat and add the carrots and potatoes. Continue simmering for 15-20 minutes until vegetables are softened.
Remove from heat. Stir in the chicken, cheese, parsley and salt/pepper if needed. Taste test!
Cover the top of the skillet with pie crust. As stated above, buy from the store or make your own. Fold the pie crust around the edges (may need to wait for the pan to cool down some) and place a couple of slits on the top or do some cute cutouts. Use a silicone brush to paint the top with an egg wash, if desired.
Bake for 35-40 minutes until crust is lightly browned. Let cool for 10-15 minutes and garnish with fresh herbs. Enjoy!