MELT butter in large skillet on medium heat. Add chicken; cook and stir 3 min. or until evenly browned. Remove from skillet; cover to keep warm.
ADD mushrooms and broccoli to skillet; cook and stir 5 min. or until mushrooms are golden brown and broccoli is tender. Return chicken to skillet. Cook and stir 3 min. or until chicken is cooked through. Add dressing: cook and stir 1 min. or until ingredients are coated and heated through.
SERVE topped with the cheese.