I'll try my best to explain how I make mine - if you need any clarification feel free to ask:
About 2 cups chopped, cooked chicken per pie - (I like a combination of light and dark but it doesn't matter)
I try to get 2 - 2 1/2 cups of the following vegetables. I simmer broccoli, carrots, leeks, celery, peas until tender but still firm in salted, boiling water. I try to chop everything pretty much the same size as the peas. If I use frozen peas I add those last after they are thawed (in microwave) as I only want to heat them. I think one time I even used some cauliflower.
I melt roughly 1/4 cup flour and a 1/4 cup butter to make a roux and cook for about 3 - 5 minutes on medium low or so. Add roughly 3 cups of milk or 1/2 and half and dissolve about 2 tsp or so of chicken base (you can use bullion cubes too if you want) Taste to see if it tastes like "chicken" and add a bit more if needed. Don't add more salt yet because the next ingredient will add some salt.
Stir in some Parmesan cheese - the kind that is grated in the tubs (not the green can) or grate your own - I'm guessing I use maybe 1 cup?
Taste at this point to make sure you have added enough salt and there is enough poultry flavor from the chicken base.
Pour in vegetables and then pour roux over vegetables. I use a double crust for this - MUCH better and keeps it very moist. Make a couple slits in top and place some foil on lower rack to catch overflows
Note that I usually make two of these and freeze one. It's a lot of chopping, dicing, and slicing and it freezes well.
Bake at 400 degrees F. for 45 minutes or until upper crust browns. You may need to foil the edges if they start to overcook.