Step 1

Bring a large pot of water to a boil and season with 2 tablespoons salt. Add pasta and cook according to the package directions. Drain and let cool slightly.

Step 2

In a large bowl, whisk together mayonnaise, sour cream, vinegar, sugar, mustard, 1 teaspoon salt and ½ teaspoon pepper. Add cooked pasta, bell pepper, celery and scallions and toss to combine. Cover and refrigerate at least 2 hours and up to 3 days. Stir in parsley before serving.