To prepare crust:
Combine flour, shortening, salt, and water, using the paddle attachment or a large fork, until all ingredients are blended. Be careful to not overwork the dough.
Divide in half. Roll out one half to line the pie plate. Set the other half aside, until filling is made.
Preheat the oven to 425 degrees.
Filling:
In a medium bowl, combine the frozen vegetables and set aside.
In a medium saucepan, melt the butter on medium heat. Once the butter is melted, stir in the flour, salt, and pepper.
Keep stirring until the mixture begins to bubble, then quickly pour the chicken broth and milk into the mixture.
Be sure to constantly stir until it begins to thicken. Remove from heat.
Add in chicken and vegetables, stirring to evenly combine the ingredients.
Pour mixture over the prepared pie crust, then roll out the second portion of remaining pie crust dough and cover the pie.
Seal the edges of the crust using your fingers to flute it, or seal the edges by pressing down with a fork. Make small slits/cuts in the top crust for venting.
Bake for 30-35 minutes until crust is golden.