In a large bowl, combine flour and salt, then cut in the cold butter until the mixture resembles coarse crumbs. Gradually add ice water, mixing until a dough forms, then divide in half and chill for 30 minutes.

Melt butter in a large skillet over medium heat, then whisk in flour and cook for one minute. Gradually add chicken broth and heavy cream, stirring until the mixture thickens.

Stir in shredded chicken and mixed vegetables into the thickened sauce, seasoning with salt and pepper to taste. Roll out one half of the chilled dough and place it into a 9-inch pie plate.

Pour the chicken mixture into the pie plate and cover with the remaining rolled-out dough, crimping the edges to seal. Cut several slits in the top crust and bake at 375°F (190°C) for 35-40 minutes, or until the crust is golden brown and the filling is bubbly.