In a small bowl, whisk together 2 tbsp / 30g (1.06 oz) mayonnaise, 2 tbsp / 30g (1.06 oz) sour cream, 0. 5 tsp onion powder, 0. 5 tsp (25 ml) garlic powder, and 1 tsp (5 ml) dried parsley until completely smooth.
Stir in 1 tbsp / 15ml of milk. If the dressing is too thick for your liking, add another tablespoon of milk until you reach the desired consistency.
In a large salad bowl, assemble the base by layering 3 cups / 150g (5.3 oz) shredded romaine, 1 cup / 150g (5.3 oz) cucumber, 0. 5 cup / 85g tomatoes, the sliced eggs, and 4 oz / 115g cubed cheddar cheese.
Add a dollop of 1 tbsp / 15g (0.53 oz) Dijon mustard to the center of the salad.
Drizzle the creamy dressing over the top, toss gently to coat everything evenly, and serve immediately.
Dry your greens thoroughly with a salad spinner or paper towels to ensure the creamy dressing clings perfectly to every leaf.