Turkey Gravy

Transfer drippings and vegetables from roasting pan from the cooked turkey in Roasted Herb Turkey and Gravy to a medium saucepan; add 3 1/2 cups chicken broth. Bring to a boil over high. Reduce heat to medium, and simmer 20 minutes. Pour mixture through a wire-mesh strainer into a bowl, pressing on vegetables to extract juices. Discard vegetables. Return broth mixture to saucepan. Whisk together flour and remaining 1/2 cup chicken broth in a small bowl; whisk into broth mixture. Bring to a boil over high; boil until reduced to about 4 cups, about 20 minutes. Serve turkey with 2 cups gravy, and reserve remaining 2 cups gravy for another use.