Wash the rosemary and thyme and dab dry. Pluck rosemary needles from the twigs and thyme leaves from the stems. Peel onions and garlic. Cut onions into slices and garlic into slices.
Peel, wash and slice the potatoes. Spread the potatoes, onions and garlic on a greased baking tray, sprinkle with the herbs, pepper and coarse salt. Drip oil over the potatoes.
Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 30 minutes. Turn the potatoes in between. Wash the chives, dab dry and cut into small rolls, except for a little garnish.
Stir yoghurt and milk until smooth and season with vinegar, salt, pepper and sugar. Stir in chives. Clean, wash and spin dry the salad. Pluck the large leaves small. Wash, clean and dice the cucumber.
Wash the tomatoes, clean them and cut them into slices. Drain the corn. Mix lettuce leaves, cucumber, tomatoes and corn. Arrange lettuce and fried potatoes on plates. Spread some dressing over the salad and garnish with chives.
Add the rest of the dressing.