Wash the potatoes and cook covered in water for about 20 minutes. Drain, quench and let cool down a little. Peel potatoes and let them cool down.
Onions peel, finely dice. Finely dice the bacon as well. Cut potatoes into slices. Heat 2 tablespoons of oil. Fry the bacon until crispy. Add half the onions and fry briefly. Stir in vinegar, 1⁄4 l water and broth, bring to the boil.
Simmer for 2 minutes. Season with salt and pepper. Mix hot with the potatoes, cover and leave to stand for at least 1 hour.
In the meantime, knead the minced meat, egg, remaining onions, breadcrumbs and mustard for the meatballs. Season with about 1 teaspoon salt and about 1⁄2 teaspoon pepper. Form approx. 12 small meatballs from the mixture.
Heat 1-2 tablespoons of oil in a frying pan. Fry the meatballs for 10-12 minutes in 2 portions while turning. Season potato salad to taste again. Serve with the meatballs.