Melt butter in large skillet over medium heat. Add onions, carrots and celery and cook about 10 minutes or until onions are translucent. Add flour and cook about a minute or two. Whisk in chicken stock. Whisk in milk. Reduce heat to low and simmer about 10 minutes.
Add the chicken, thyme, sherry, peas, salt and pepper. Taste and adjust seasonings if needed.
Filling is complete. Pot pie can be made in casserole dish with top crust added, or 2 deep dish pies - single or double crust, or 6 10-oz ramekins with top crust.
Add filling and cover with pie crust. Cut vent for steam to escape. Bake at 400° for 25 minutes or until pastry is golden and filling is bubbling.
Hint: You may want to cook on a foil lined cookie sheet in case it bubbles over.
Note: The filling freezes well. I freeze in individual serving sizes, then just thaw, top with crust and bake.
