This is basically a light chicken stew wih a sauce of butter. flour, and chicken stock, with some kind of pastry included.

Chicken:
Use just breast and thigh meat. Poach your chicken or roast it in the oven, saving the stock or drippings for later. OR pulled chicken or diced are both available ready to use frozen through food/restaurant suppliers such as Sysco.

Old cook's trick. If you are starting from scratch, roast whole turkey is much easier than lots of chickens.

Veggies
Wide variation in what vegetables are used. For each whole chicken (about 6 cups meat), I use between 2-3 pounds total. Frozen might include cut green beans, corn, peas. Fresh cut, large diced onions, carrots and celery. The celery really freshens it. For a quickie, frozen mixed veggies with extra onions, maybe bell pepper and celery.

Sweat the chosen veggies in butter with bay leave, thyme, sage and black pepper. Make the gravy/sauce right over the veggies. Add chicken stock and/or drippings, thicken with roux, I like to use 1 lb. of butter and 1 lb. of flour per 2 gallons of stock and then adjust when it comes to boil. Check for seasoning. If you have used chicken bouillon paste or cubes in your stock, you will not need salt.

To assemble in large, 2 1/2 in deep chafers, cut breast meat and thigh meat to size. amounts, place them in pans and cover with the velute. These pans hold 1 1/2 gallons of liquid so depending on how much chicken your using you need 3/4 to 1 gal of velute per pan.

In roasters, I NEVER use a bottom crust.

Cover with a pie crust made from, 3 parts flour, 2 parts shortening, 1 part water, a little salt and a little sugar. Brush crusts with milk. Bake until crust is cooked through and filling is bubbling.

2 lbs of crust will cover a standard chafer pan well, you can weigh out 2 1/2 lb. balls and cut of the extra.
Used puff pastry squaresbrushed with egg wash and herbs for the crust. Ladle the chicken mix off the steam table and plop a crust on it.

You can also use puff pastry sheets or squares.

Alternative assembly (might work better in roasters, as pastry tops don't do too well in thesem because they cook more moist).

Store the chicken stew cold. Prebake pastry squares or puff pastry squares fully. Heat the stew to boiling, plate with a cap of just re-toasted pastry, drizzle a little sauce over the crust. You can put a second piece under the hot stew if the diners like more crust.

Brush crusts with milk.
Bake until crust is cooked through and filling is bubbling.

A full steamer pan usually makes 16 large servings.