1 sheet of puff pastry, thawed*
Anyway, if you're not comfortable with roasting chicken, here's how I do it:
Cover a baking sheet with aluminum foil, lay your chicken breasts on it, drizzle with a little bit of olive oil, sprinkle with salt and seasonings of your choice, roast at 425* for 40 minutes (for bone-in chicken), or 350* for 35 minutes (for boneless chicken). Let rest, cool, and shred up!
While my veggies are cooking, I shred up the chicken, and place it in a bowl, then set it aside. Once the carrots and celery are soft, add in the fresh chopped parsley, and mix well.
Once your mixture has turned light brown, carefully add in your spices, chicken stock, and cream, and let this reduce over medium heat, stirring every couple of minutes to make sure the bottom doesn't burn, until it has thickened to your liking. I like mine a little soupy, but feel free to let it continue to thicken!
Once your gravy has thickened to your liking, taste for salt and pepper, then add in the chicken and veggies, stir to combine, and pour everything into a 9"x13" baking dish.
Oh boy! This is so yummy!
After its rolled out, lay it down on top of your baking dish, folding the corners up back onto the pastry so they won't burn, and brush the top with an egg wash (some people add water or milk to their egg, and that's fine. I just use straight beaten egg for my egg wash), then cut slits on the top of the pastry, so that the steam can escape as the pot pie bakes.
I recommend baking this for 25 minutes. I baked mine for closer to 30, because I got caught up doing something else, so it got a little bit darker than I normally like, but that's okay! Still tastes good, right? The puff pastry bakes up light and fluffy and looks so impressive when you pull it out of the oven! Let it sit for 10-20 minutes, then serve it up and enjoy! Yum!