Bring a large pot of salted water to a boil and add the rotini pasta. Cook according to package directions until al dente, then drain and rinse with cold water to stop the cooking process and cool it down quickly. Set the cooled pasta aside—this gives you time to prepare the other components while it chills.

While the pasta cooks, dice the celery and carrots into bite-sized pieces, keeping them roughly the same size so they cook and distribute evenly throughout the salad. Slice the green onions thinly, separating the white and light green parts from the darker green tops—you'll use the tops as garnish at the end.

In a medium bowl, whisk together the ranch dressing, buffalo sauce, blue cheese, and garlic powder until smooth and well combined. I like to whisk this vigorously for about 30 seconds to help break down any clumps of blue cheese and fully incorporate the buffalo sauce—this ensures the dressing coats everything evenly without any streaks of sauce.

In a large bowl, combine the cooled pasta from Step 1 with the cooked chicken, diced celery, and diced carrots. Pour the dressing from Step 3 over the mixture and toss thoroughly until everything is evenly coated and well combined. The salad can be served immediately or chilled for up to 2 hours before serving.

Divide the pasta salad among serving bowls and top with the reserved sliced green onion tops for a fresh garnish and a mild onion flavor. I find that adding the green onions just before serving keeps them bright and crisp rather than wilting them into the salad.