Boil eggs hard in about 10 minutes. Then quench briefly under cold water and cool down. Cut tomatoes in half or in quarters depending on size. Cut gherkins into fine slices. Mix sour cream, whole milk yoghurt, some cucumber water and possibly some mustard until smooth. Season salad dressing with salt and pepper to taste.
Peel the eggs and cut them into slices or chop them roughly. Mix with cucumber slices, ham cubes and salad dressing. Pluck the chervil leaves from the stems, wash the green salad, drain on a sieve and pluck into bite-sized pieces. Put the lettuce leaves in a small bowl and arrange the egg salad on top. Sprinkle with chervil leaves