This is a "grandma recipe"—so there's lots of room for interpretation. Also: This is just the filling. You can make individual pot pies or a casserole—just cover with homemade or store-bought pie crust. You can also place pie crust on bottom of pie if you like. See what we mean?
In a large pot, melt the butter and sauté the onions (if using) over medium-low heat until translucent. Add the flour and cook over low heat, stirring constantly for about 2 minutes (You are making a rue).
Add the chicken broth and bouillon. Simmer over low heat, stirring until thickened. Add salt, pepper and heavy cream. (Taste to make sure it tastes chicken-y enough; add bouillon, salt, pepper to taste.) Add cubed meat, potatoes, carrots, peas, onions, parsley. Mix well.
You can make individual pot pies or casserole: Just cover with pie crust. You can also place pie crust on the bottom, if you like.
Place on baking sheet and bake at 375 for about 1 hour until the top is golden brown and the filling is bubbling hot.