In a small bowl, combine the sour cream, mayonnaise, white vinegar, salt and pepper. Set aside.

In a large bowl, combine radishes, cucumbers, scallions, dill, and parsley. Mix well.

Add dressing and mix to incorporate right before serving. Garnish with thinly sliced scallion.

Chef's Note: Adding the dressing too far in advance will cause the juices in the cucumber and radish to run and make the salad too watery.