Wash the potatoes and boil in water for about 20 minutes. Quench potatoes, peel and let them cool down
Soak half of the pretzels in beer. Finely dice the remaining pretzels and roast them all around in the hot butter
Onions peel, finely dice. Cut potatoes into slices. Boil 1/8 l water. Dissolve stock in it. Add vinegar and half onions. Stir in 2-3 tsp. mustard and crème fraîche. Season with salt and pepper. Pour over the potatoes, mix carefully
Clean, wash and slice the radishes. Wash the chives and cut into small rolls. Fold both into the potatoes. Leave everything to stand for about 30 minutes.
Knead minced meat, squeezed pretzels, egg, rest of onions and 1 tsp. mustard. Season with salt and pepper. Knead in roasted pretzels. Form approx. 8 meatballs from the mixture
Fry the meatballs in hot oil for 6-8 minutes on each side. Cut cheese into strips. Cut the meatballs crosswise and press the cheese into the incisions. Cover and fry for another 2 minutes. Season potato salad again and arrange with the meatballs. Sweet mustard goes well with it