Preheat oven to 350°F.
Combine the chicken broth and 1/4 cup of the milk in a small saucepan. Bring to a low boil and then reduce heat to low.
Meanwhile, in a small bowl, whisk the flour, seasonings, and remaining 1/2 cup milk until smooth. Pour the flour mixture into the saucepan with the broth and stir continuously, whisking as the mixture simmers over low heat. Continue to whisk until thick, about 5-10 minutes.
Combine chicken, soup, sour cream or yogurt and poppy seeds in a 3-quart baking dish. Mix the crackers and melted butter together in a bowl, and sprinkle on top of the chicken.
Bake for 25-30 minutes, until bubbly around the edges. Serve over rice.
Source: Family friend, Jessamyn :)