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.