In saucepan, cook onion in butter or margarine until tender. Stir in flour, then water and bouillon. Cook and stir until thickened. Remove from heat and add sour cream. Make sure sour cream is at room temperature before adding.
Combine 2 cups of the sauce with the chicken, 1 cup of cheese, chilies, and cumin. Place chicken mixture on tortillas and roll, folding burrito-style.
Arrange in greased 13x9 baking dish. Top with remaking sauce and cheese. Bake at 350 for 25 minutes or until hot. Garnish as desired. Refrigerate left-overs.