Preheat the oven to 450ºF.
Butterfly each of the chicken breasts open and cut into two thinner pieces so you have a total of 4 pieces of chicken.
Cut 4 large pieces of heavy-duty foil. Place one piece of chicken in the center of each piece of foil. Top with 1 tablespoon of Italian dressing, ¼ of the mushrooms, ¼ of the basil, and ¼ of the tomatoes. Season with salt and pepper. Bring up 2 sides of the foil and seal. Fold the opposite edges to form a packet. There should be some room in the package for heat circulation. Repeat with the remaining ingredients.
Place the foil packets on a baking sheet, and place in the oven. Bake for 15-20 minutes, or until the juice of the chicken is no longer pink, and when a thermometer inserted in the thickest part of the breast registers 165ºF.
Fold back the foil of each packet and top with the Parmesan cheese. Add more basil, if desired.
