Preheat oven to 375 degrees. Sprinkle chicken with poultry seasoning and bake at 375 degrees for 20-23 minutes, or until cooked through to a temperature of 165 degrees. Cool chicken and shred.
Turn oven down to 350 degrees. Sauté broccoli, onions and mushrooms in butter. Add salt and pepper to taste.
Stir together cooked rice, vegetables, chicken and cheddar cheese. Stir in sour cream, Ranch dressing and chicken broth. Place in casserole dish and top with Italian cheese.
Bake uncovered at 350 degrees for 25-35 minutes or until cheese is melted and casserole is heated through.