Heat oven to 375°. Heat chicken, pasta sauce and broccoli to boiling in 3-quart saucepan, stirring frequently. Spread half of mixture in ungreased square pan, 9x9x2 inches.
Stir baking mix, milk and sour cream until blended. Pour half of batter over chicken mixture in pan. Spread with remaining chicken mixture; top with remaining batter. Sprinkle with cheese.
Bake uncovered about 35 minutes or until toothpick inserted in center comes out clean.