Wash the potatoes and boil in water for about 20 minutes. Cook frozen peas in boiling water for about 3 minutes, drain, quench and drain.
For the meatballs, peel and finely dice the onion. Knead minced meat, diced onion, breadcrumbs, 6 tbsp. water, egg and mustard. Season with salt and pepper.
Form approx. 50 walnut-sized balls from the chopped mass. Heat the oil in portions in a pan. Fry the meatballs in the oil for about 6 minutes each.
For the sauce, wash the dill, shake dry and chop finely. Mix yoghurt, sour cream, mayonnaise and dill. Season to taste with vinegar, salt and pepper.
Drain the potatoes, quench and let them cool down. Remove meatballs from the pan and let them cool down. Halve potatoes according to size. Mix potatoes, meatballs, peas and approx. 2⁄3 of the dill sauce. Add the rest of the sauce.