Cook potatoes with skin in boiling water for about 20 minutes. Drain, rinse with cold water, peel and let cool off.
Finely dice the gherkins. Peel and finely dice the onions. Wash chives and parsley and shake dry. Cut the chives into small rolls. Chop parsley finely.
For the vinaigrette, mix vinegar with 1 tablespoon of mustard, salt and pepper and fold in 2 tablespoons of oil. Stir in half each of the gherkins, onions and herbs.
Cut the potatoes into slices. Heat clarified butter in a large pan. Fry the potatoes until golden brown and crispy. Finally fry 1 tsp. caraway.
In the meantime, mix mayonnaise with yoghurt and 1 tablespoon of mustard for the tartar sauce. Stir in the rest of the cucumber, onions and herbs. Season tartar sauce with salt and pepper.
Mix the hot potatoes with vinaigrette and season to taste again. Roughly pluck the roast beef and mix loosely with the salad. Arrange the salad and serve with the tartar sauce.