Saute onion and celery: In a large skillet heat the olive oil over medium heat. Add the onion and celery and cook for about 3 minutes until the onion is soft and translucent.
Add chicken and cook: Add the chicken to the skillet and stir. Season with salt, pepper, red pepper flakes and thyme then stir. Cook for another 5 minutes until the chicken is no longer pink.
Add frozen peas, carrots and potatoes: Add the frozen peas and carrots. Stir in the potatoes and cook for another 5 minutes. Add the cream of mushroom soup and chicken broth. Stir in the parsley.
Cover with puff pastry: Cover the skillet with the puff pastry sheet then tuck in the edges. Brush with egg wash, then cut a couple slits in the center of the pie.
Bake: Bake for 45 minutes or until the crust is golden brown.
Slice and serve warm.
I used a 10 1/2 inch skillet for this recipe.This would also work in a 9 x 13 inch pan using the same baking instructions.For a creamier filling go ahead and use 2 cans of cream of mushroom soup.To freeze this, I would recommend freezing it before baking it, so after you add the puff pastry, cover it with plastic wrap or aluminum foil and place it in the freezer. When ready to cook, remove from freezer, brush with the egg wash and place in the oven.To store leftovers, store in airtight container in the refrigerator for 3 to 4 days max.Please keep in mind that nutritional information is a rough estimate and can vary greatly based on products used.