PREHEAT oven to 350°F. Melt butter in medium saucepan on medium heat. Stir in flour and Seasoning Mix with wire whisk; cook and stir 1 minute. Add milk, stirring constantly, until slightly thickened, about 3 minutes. Stir in sour cream and chicken stock. Simmer 3 minutes or until slightly thickened. Remove sauce from heat and set aside.
MIX 1/2 cup of the sauce, shredded chicken, corn, and 1 1/2 cups of the cheese in medium bowl. Spoon about 1/2 cup of the chicken mixture onto each tortilla. Roll tortillas around filling; place seam-side down in 13x9-inch baking dish sprayed with no stick cooking spray. Pour remaining sauce over enchiladas. Sprinkle with remaining cheese.
BAKE 25 minutes or until heated through and cheese is melted. Drizzle with Frank’s RedHot® Sauce and sliced green onions, if desired.