Place the chicken breasts in a large plastic storage bag and pour Italian dressing on top. Place into the fridge and marinate overnight.
To prepare, remove the chicken from the marinade and discard the marinade. Season the chicken on both sides with Mediterranean Herb or Rotisserie chicken seasoning.
Drizzle a large skillet with olive oil and add 2 Tbsp of butter or light butter.
Sear the chicken pieces for 3-4 minutes on each side or until the juices run clear. Adjust the time based on the thickness of the chicken breasts. Remove to a platter, cover and keep warm.
In the same pan, saute the mushrooms for 2-3 minutes then add the sliced green onions and minced garlic. Add additional olive oil, if needed. Season with salt and black pepper to your taste.
Add the Worcestershire sauce and red pepper flakes. Cook for around 2-3 minutes until the onions begin to soften.
Add the baby spinach. Saute until the spinach wilts and the juice evaporates.
Spoon sauteed vegetables on top of chicken pieces. Sprinkle each with Asiago cheese. Sprinkle the tops with additional Mediterranean Herb or Rotisserie chicken seasoning, if desired.
Transfer skillet to the oven or place chicken pieces on a prepared baking sheet if skillet used isn't oven safe. Broil for 2 minutes or until the cheese melts.