Preheat your oven to 375 degrees F.

Warm about 1 - 2 tbsp oil in a large skillet over low-medium heat.

Cut the chicken into 1 inch chunks, then add it to the skillet. Season with the salt and pepper.

Cook until just before the chicken browns (about 5 minutes or so), don’t brown it. The chicken can actually be slightly pink because it’s going to bake in the oven for about 1 hour. Doing it this way will keep the chicken tender. Transfer the chicken to a bowl and set aside.

In the same skillet you used to cook the chicken, add 1 tbsp oil then add the onions, celery, carrots and potato. Cook until soft, about 5 minutes.

Then add the thyme, bay leaf and flour. Stir while cooking for 1 minute.

Add the chicken broth to the mixture, bring it to a light boil, stirring constantly until the mixture thickens. This takes about 4 minutes.

Once thickened, add the chicken, frozen corn or peas and the cream. Stir.

Remove the bay leaf.

Transfer the chicken pot pie filling into a deep 9-inch pie plate or oven proof casserole dish.

Add the thawed puff pastry sheet (or homemade crust) on to the top of the pie dish, making sure to cover the edges.

Use a sharp knife to cut vents into the pie crust dough (I like to put a few 1 inch small slits into my crusts).

Brush the pastry with the beaten egg wash.

Place the pie in the oven, and put a baking sheet on a separate rack under the pie to catch any drippings.

Bake for about 1 hour 30 minutes, or until the crust is golden brown and the filling is bubbling.

Tip! If the crust looks like it's darkening too quickly, tent it with a piece of aluminum foil.

Let sit for a few minutes before serving.