Preheat the oven at 400 degrees F.
Season the chicken thighs with salt, pepper, and spices on both sides. Cook them in a hot, oiled skillet for 5–6 minutes per side. After flipping, I like to cover the pan and lower the heat to medium-low to keep the chicken tender and juicy.
Once fully cooked through, remove the chicken from the skillet and shred it using two forks or an electric mixer. Set the shredded chicken aside.
Add more oil to the same skillet you cooked your chicken in if needed and add the onions, celery, and carrots. Cook for 6-7 minutes over medium low heat while stirring occasionally.
Stir in the garlic, rosemary, thyme, and cook for 30 seconds.
Add the butter and scrape the bottom of the pan, then whisk in the flour. Cook this for a few minutes.
Add the chicken stock and heavy cream, cook for 10-15 minutes or until the sauce thickens. Once the sauce thickens, add the parmesan cheese, Worcestershire sauce, shredded chicken, corn, and peas. Allow it to simmer for a few minutes. Season generously with lots of salt and pepper.
Press one puff pastry sheet into a pie dish, pour the filling into the dish and lay the second puff pastry sheet over the top (if not doing the lattice style.)
Trim excess pastry and seal the edges. Cut a few small slits for steam to escape and brush the top with beaten egg.
Bake for 30–35 minutes or until the pastry is golden brown and puffed. Once it comes out of the oven, sprinkle the top with coarse salt and let it rest for 10 minutes before slicing into it. Enjoy!