Boil eggs in boiling water for 8-10 minutes until hard. Coat a baking tray with oil, sprinkle with coarse salt and caraway seeds. Wash the potatoes, cut them in half and spread them on the baking tray with the cut surface facing down.
Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 20-30 minutes. Wash the herbs, pluck the leaves from the stems and chop them. Cut cress from the bed. Drain eggs, rinse with cold water, peel, halve and, except for one half, remove the egg yolk.
Puree yoghurt, sour cream, oil, lemon juice, egg yolk, herbs, except for a tablespoon for garnishing, and mustard with the blender. Peel onion and garlic and cut into fine cubes. Chop egg white and gherkin finely and add to the sauce with onion and garlic.
Season the sauce with salt, pepper and sugar. Pour the sauce into a bowl. Cut half the egg into cubes and sprinkle the remaining herbs over the sauce. Arrange potatoes on a plate and garnish with parsley and dill.