You can make this pot pie one of two ways: either as a skillet pot pie with a biscuit crust (using my Pumpkin Biscuit recipe), or as a more traditional pot pie with a rolled pastry crust. I prefer the biscuit method because it’s easier and makes for a quicker dinner, but either is good!
3 tablespoons butter or olive oil, or a combination (I use a combination)
3 stalks celery, finely diced
1 medium onion, finely diced
4 medium carrots, finely diced
1 medium sweet potato, finely diced
6 oz. mushrooms (button, cremini, or any mixture you like), quartered
1/4 cup all-purpose flour (whole wheat is fine, too)
1 1/2 tsp. dried thyme
salt and pepper to taste
2 cups Slow Cooker Chicken Stock (you could also use store-bought)
4 cups diced cooked chicken
1 cup frozen peas, unthawed
1/3 cup half and half

Pumpkin Biscuits OR:
2 cups all-purpose flour
1/2 cup very cold butter, cut into pieces
1 tsp salt
3/4 cup pumpkin puree
1/2 tsp nutmeg
6-10 tablespoons ice water

To make the crust: Combine flour, salt, and nutmeg in a food processor; pulse to mix.  Add the pumpkin puree and butter and pulse until the crust starts to come together (it will still be somewhat crumbly).  With the machine running, add the water, a tablespoon at a time, until the dough starts to make a ball and comes away from the sides of the bowl.
Turn the dough out onto a lightly floured surface, divide in half, and pat each half into a disk.  Wrap the dough in plastic and put in the refrigerator to chill for 30 minutes-1 hour.  (You’ll only need a top crust, so I’d freeze one of these, or find another use for it.)  When you’re ready to use it, take one of the disks out of the refrigerator and roll out to about 1/4 inch thickness.  Place over the pot pie filling and bake as instructed below.

To make the filling:
In a large skillet, melt the butter/oil over medium heat.  Add the onions and celery and sweat for about 3 minutes, until they start to soften.  Add the carrots and sweet potatoes and sprinkle with a little salt.  Cook for about 8 minutes, until all the vegetables have started to soften slightly and release a bit of liquid.  Add the mushrooms, thyme, salt, and pepper.  Cook, stirring, for about 2 minutes more.

Sprinkle the vegetables with the flour and cook for 1-2 minutes (the flour will start to form a paste).  Gradually pour in the chicken stock, using a spoon to scrape the bits off the bottom of the pan; cook, stirring constantly for 2-3 minutes to keep the sauce from getting lumpy.  Reduce the heat to a simmer and let the vegetables and sauce cook together for about 5 minutes, until the sweet potatoes and carrots are tender and the sauce has started to thicken.  Add the cooked chicken and the frozen peas and stir to combine.
Simmer over low heat for an additional 5 minutes to warm the chicken and peas through.  Stir in the half and half to add richness and creaminess to the dish, taste, and adjust the seasonings as needed.  At this point, you may either top with warm biscuits and serve, or pour the filling into a 2-quart casserole dish, add the top pastry crust (cut a few steam vents in the crust to prevent explosions), and bake at 425 degrees for about 40 minutes (watch carefully to be sure the crust doesn’t burn).