01 - Bring a large pot of salted water to a boil. Cook elbow macaroni until al dente following package instructions. Drain in a colander and rinse under cold running water to cool completely.
02 - In a large mixing bowl, combine cooled macaroni, celery, red bell pepper, red onion, carrots, and peas.
03 - In a separate small bowl, whisk together mayonnaise, sour cream, Dijon mustard, apple cider vinegar, sugar, salt, and black pepper until the mixture is smooth.
04 - Pour the dressing over the macaroni and vegetable mixture. Stir gently to coat all ingredients evenly.
05 - Fold in parsley and chopped hard-boiled eggs if using.
06 - Cover the bowl and refrigerate for at least 1 hour to allow flavors to meld.
07 - Stir the salad gently before serving and adjust seasoning if necessary.