Wash the potatoes and cook in boiling salted water for about 20 minutes. In the meantime, clean, wash and cut the peppers into pieces. Soak rolls in cold water. Peel onions, finely chop one onion, coarsely chop the remaining onions. Wash the cucumber and grate coarsely.
Peel garlic and press it through a garlic press. Mix yoghurt, quark, cucumber and garlic and season with salt and pepper. Knead minced meat, squeezed roll, egg, mustard, salt, pepper, paprika powder and fine diced onion. Cut feta cheese into 8 cubes. Divide minced meat into 8 parts, form into dumplings, press flat, add 1 cube of sheep's cheese each and form into dumplings again. Drain potatoes, rinse with cold water and cut into quarters. Heat 2 tablespoons of oil in a frying pan and fry the dumplings for about 10 minutes while turning. Heat 1 tablespoon of oil in a second pan and fry the potatoes in it until golden brown, turning them over. Season the potatoes with salt and pepper. Heat the rest of the oil in a saucepan, fry the peppers and remaining onions in it, deglaze with stock, let it stew for about 5 minutes and season with salt, pepper and paprika.
Drain potatoes, rinse with cold water and cut into quarters. Heat 2 tablespoons of oil in a frying pan and fry the dumplings for about 10 minutes while turning. Heat 1 tablespoon of oil in a second pan and fry the potatoes in it until golden brown, turning them over. Season the potatoes with salt and pepper. Heat the rest of the oil in a saucepan, fry the peppers and remaining onions in it, deglaze with stock, let it stew for about 5 minutes and season with salt, pepper and paprika. Arrange potatoes, meatballs, paprika vegetables with a blob of quark on a plate and garnish with parsley leaves as desired. Serve the rest of the quark extra