Make the sauce; In a small saucepan, melt 1 tablespoon butter. Stir in flour, curry powder and paprika; cook until the flour and spices lose their raw smell, 1 to 2 minutes. Add the chicken broth and milk. Bring to a simmer and cook, stirring, until thickened, 5 minutes. Stir in the mustard and mustard seeds; simmer to develop the flavors, about 5 more minutes. Whisk in the remaining 1 tablespoon butter; add 1/2 teaspoon salt, and pepper to taste. Keep warm until ready to serve.