Soak the buns. Peel, wash and quarter the potatoes. Cook in boiling salted water for about 20 minutes. In the meantime peel onions. Cut one onion into fine rings. Peel the cucumber and cut it into thin slices.
Season vinegar with salt, pepper and sugar. Add 2 tablespoons of oil. Pluck the dill flags and add to the marinade. Fold in onion rings and cucumber slice. Finely dice the remaining onion. Knead with minced meat, egg, bread roll and mustard.
Season with salt and pepper and form into dumplings. Fry in 2 tablespoons of hot oil all around for about 8 minutes. In the meantime drain the potatoes. Warm the milk, add it and mash the potatoes finely. Season to taste with salt and nutmeg.
Arrange mashed potatoes, cucumber salad and meatballs in portions with the cranberries. Serve garnished with dill.