Combine chicken broth and 1/2 cup milk in large saucepan & bring to a low boil.
In small bowl, whisk flour and seasonings into 1 cup milk until thick, smooth mixture forms.
Pour the flour and milk mixture into the saucepan with the broth mixture over low heat and stir continuously, whisking as the mixture simmers. Continue to simmer and stir/whisk until the mixture is smooth and thick, 5-10 minutes. The mixture will thicken a bit as it cools.