Preheat over to 350 degrees. In large skillet, cook butter and onion until tender. Stir in flour and then hot water and bouillon. Cook and stir until thickened and bouillon dissolves. Remove from heat. Stir in sour cream. Set aside. Reserve 1 cup sauce for step 2.
In large bowl, combine chicken, 1 cup sauce, 1 cup cheese, chilies, and cumin. Mix well.
Dip corn tortillas into hot sauce to soften. Fill with chicken mixture. Roll up. Arrange in greased 13x9 pan. Spoon remaining sauce over top. Sprinkle with remaining cheese.
Bake for 25 min. or until bubbly. Garnish as desired.