1In medium bowl, toss chicken strips and dressing mix; set aside.
2In large skillet, heat oil over medium-high heat. Add mushrooms and onion; cook and stir until mushrooms start to brown and onion starts to soften. Add chicken; cook about 5 minutes, stirring frequently, until chicken is no longer pink in center.
3Set oven control to broil. Split buns, but don’t cut all the way through. Open buns and place cut sides up on ungreased cookie sheet. Spoon chicken mixture evenly onto bun bottoms; top with cheese (cut slices in half to fit, if necessary).
4Broil with tops 4 to 6 inches from heat about 2 minutes or until bread is toasted and cheese is melted.