In a small bowl, whisk together the mayonnaise, sour cream, Dijon mustard, and apple cider vinegar. Add salt and black pepper to taste and stir until creamy. Set aside to meld for at least 10 minutes.

In a large bowl, combine cooked pasta, cubed chicken, and crumbled bacon. Add halved cherry tomatoes, thinly sliced red onion, and chopped romaine lettuce. Toss gently to evenly distribute ingredients.

Sprinkle shredded cheddar cheese over the mixture. Fold in cubed toasted bread or croutons without squashing the ingredients.

Drizzle the prepared dressing over the salad and gently toss until all ingredients are well-coated.

Chill in the refrigerator for at least 30 minutes before serving. Garnish with freshly chopped parsley or chives if desired.