Begin by bringing a large pot of salted water to a rolling boil. Add in the rotini pasta and cook according to package instructions until al dente, usually about 8-10 minutes. Once cooked, drain the pasta in a colander and rinse it under cold water to stop the cooking process.

In a mixing bowl, whisk together mayonnaise, Greek yogurt, Parmesan cheese, lemon juice, Dijon mustard, and minced garlic. Stir until the mixture is smooth and creamy, and season with salt and pepper to taste.

In a large serving bowl, combine the cooled rotini, shredded cooked chicken, and chopped romaine lettuce. Pour the creamy dressing over the top and gently toss everything together until well coated.

Add a generous handful of croutons on top just before serving, and give the salad a gentle toss to incorporate the croutons.