Clean, peel and slice the carrots and cook in salted boiling water for about 10 minutes, drain well.
Soak the rolls. Finely dice 1 onion, cut the rest into wedges. Clean and halve the mushrooms. Cut the cucumber into slices.
Knead the minced meat, diced onion, squeezed bread roll, egg and mustard. Season to taste with salt, pepper and paprika. Form dumplings from the dough with moistened hands.
Heat the oil in a high pan and fry the mushrooms in it, turning. Take out of the pan. Fry the onion wedges in the oil and remove them. Put the meatballs in the pan and fry for 8 to 10 minutes, turning over a medium heat, remove.
Deglaze the frying fat with vegetable stock, 100ml cucumber stock from the glass and cream and bring to the boil. Stir in the sauce thickener (cornstarch), bring to the boil again, season with salt, pepper, paprika and sugar to taste. Add meatballs, onion wedges, mushrooms, cucumber and carrots to the sauce and bring to the boil again. Finely chop the parsley and sprinkle over it.