Soak rolls in cold water. Clean and wash spring onions and cut into thin rings. Wash herbs, dab dry and chop. Chop, squeeze out the bread roll, half the spring onions, knead the herbs and the egg. Season with salt and pepper.
Form 4 large or 8 small meatballs from the minced meat and fry in hot oil, turning for 10-15 minutes. In the meantime, clean, peel and chop the kohlrabi and carrots. Clean and wash the cauliflower and cut into small florets. Cook vegetables in boiling salted water for about 15 minutes. Let them drip off, collecting the cooking water. Heat the fat, stir in the flour and sweat it. Gradually stir in 1/4 litre vegetable water and cream. Let simmer for 5 minutes at low heat. Add lemon juice and zest to the sauce, season with salt and pepper. Add vegetables.
Heat the fat, stir in the flour and sweat it. Gradually stir in 1/4 litre vegetable water and cream. Let simmer for 5 minutes at low heat. Add lemon juice and zest to the sauce, season with salt and pepper. Add vegetables. Arrange the meatballs on the vegetables. Sprinkle with the remaining spring onion rings