1. Preheat oven to 400°.
2. Combine 1/4 cup cheese and next 7 ingredients (through chiles) in a large bowl, stirring just until moist. Pour mixture into a 13 x 9–inch baking dish coated with cooking spray.
3. Bake at 400° for 15 minutes or until set. Pierce entire surface liberally with a fork; pour enchilada sauce over top. Top with chicken; sprinkle with remaining 3/4 cup cheese. Bake at 400° for 15 minutes or until cheese melts. Remove from oven; let stand 5 minutes. Cut into 8 pieces; top each serving with 1 tablespoon sour cream.