Wash the potatoes and cook in boiling water for about 20 minutes. Boil eggs in boiling water for about 10 minutes until hard. Quench eggs under cold water, peel, halve and let them cool down.
Drain the potatoes, rinse with cold water and peel. Wash and peel the asparagus and cut off the woody ends. Cook the asparagus for 15-20 minutes in boiling salt-sugar water. For the sauce, wash the herbs, dab dry and chop very finely except for some cress for garnishing.
Pass 3 egg yolks through a sieve. Finely chop the egg white. Mix mayonnaise, yoghurt, egg yolks and mustard. Stir in egg whites and herbs. Season to taste with sugar, salt and pepper.
Heat the oil in a frying pan and fry the potatoes for about 5 minutes, turning them until golden brown. Season with salt. Drain the asparagus and let it drain. Chop remaining egg yolk. Arrange asparagus with green sauce, potatoes and ham.
Serve sprinkled with egg yolk and cress.