For the egg salad, hard boil the eggs and quarter them. Wash and dice the tomatoes. Cut onion into fine rings.
Wash radishes and cucumber and cut into bite-sized pieces. Wash lettuce.
Dry in salad spinner and mix with eggs, tomatoes, onions, radish and cucumber pieces.
Mix yogurt, salt, pepper, mustard and oil. Marinate the egg salad with it and serve sprinkled with cress.