For the salad, cover the potatoes and cook them in water with caraway seeds for about 20 minutes. In the meantime cut cucumbers into slices. Peel and finely dice onions. Mix cucumber water, vinegar and 2 tsp. mustard.
Season with salt, pepper and 3 teaspoons of sugar. Fold in the oil. 2⁄3 Stir in the onion cubes.
Drain the potatoes, rinse with cold water, peel them and let them cool down a little. Peel, quarter, core and cut apple into small pieces. Cut lukewarm potatoes into slices. Mix with cucumber, apple and vinaigrette.
Leave to steep for 3-4 hours.
Soak rolls in cold water. Wash parsley, shake dry and chop finely. Knead well with minced meat, squeezed out roll, rest onion cubes, eggs and 2 teaspoons mustard. Season with 1 tsp salt and pepper and 1⁄2 tsp paprika.
Cut the cheese into 8 cubes. Form 8 meatballs from the minced mass with moistened hands, pressing 1 cheese cube each into the middle. Heat 2 tbsp. clarified butter in a frying pan. Fry the meatballs on each side at medium heat for 5-6 minutes.
Wash the chives, shake dry and cut into fine rolls. Fold into the potato salad. Season again with salt and pepper. Serve with the meatballs.