Spray an outdoor grill with non-stick spray and preheat to medium-high heat. Season both sides of the chicken with salt and pepper. Cook the chicken for about 4-6 minutes per side, or until the internal temperature is 165 degrees. Chicken is done if juices run clear when pierced with a fork. Remove the chicken from the grill to a plate; cover and allow the chicken to rest for 3 minutes. Cut into bite sized cubes.
Meanwhile, bring a large pot of salted water to a boil. Cook pasta until al dente, drain and rinse with cool water.
In a small bowl, whisk together the mayonnaise, sour cream, garlic, anchovies. lemon juice and Worcestershire sauce.
In a large bowl, toss half of the dressing with the pasta and refrigerate for 30 minutes. (Also refrigerate remaining dressing)
Add remaining dressing, lettuce, tomatoes, green onions, Parmesan cheese, black pepper and croutons if using, gently toss to combine.