Combine eggs, mayonnaise, lemon juice, celery, scallions, and parsley in a medium bowl. Using your hands, squeeze eggs through your fingers, mixing contents of bowl until reduced to desired consistency; alternatively, smash and mix with a firm whisk. Season generously with salt and pepper. Serve with sliced radishes, lettuce, and bread to make sandwiches, or store in a sealed container in the refrigerator for up to 3 days.