Wash the potatoes and cook for 20-25 minutes until soft. Bring stock and vinegar to the boil. Drain potatoes, rinse briefly under cold water, peel and cut into thick slices. Add stock and vinegar to the potatoes. Let the salad stand for 1-2 hours.
For the meatballs peel and finely dice the onion. Knead minced meat, eggs, breadcrumbs, 4 tablespoons milk, onion and mustard and season with salt and pepper. Shape 12 meatballs with wet hands and chill. Blanch peas in boiling salted water for about 2 minutes, then rinse with cold water. Clean and wash the radishes and cut them into small slices. Put the corn in a sieve and let it drain. Clean, wash and cut spring onions into rings. Mix yoghurt and mayonnaise, season with salt and pepper. Add radishes, peas, corn, spring onions and yoghurt sauce to the potatoes.
Put the corn in a sieve and let it drain. Clean, wash and cut spring onions into rings. Mix yoghurt and mayonnaise, season with salt and pepper. Add radishes, peas, corn, spring onions and yoghurt sauce to the potatoes. Season salad again with salt, pepper and possibly a little vinegar. Heat the oil in a pan and fry the meatballs on each side for about 4 minutes
1 hour waiting time