Bring a large pot of lightly salted water to a boil. Add the elbow macaroni and cook for about 8 minutes until tender yet firm. Drain the pasta and rinse with cool water.

In a large bowl, whisk together the mayonnaise, sour cream, apple cider vinegar, white sugar, dry mustard, salt, and pepper. Taste and adjust seasonings as needed. Add the cooled pasta, green onions, celery, red bell pepper, peas, and parsley.

Stir until all ingredients are well mixed. Cover the bowl with plastic wrap and refrigerate for at least 2 hours before serving. Garnish with additional parsley.