To prepare the broth, start with the preparation of the vegetables, washing and drying them accurately. Peel the onion, carrots, and potatoes. Clean the celery. Combine all the whole vegetables and the oil in a large pan. Add salt and tomato paste and cover everything with water. Cook on a medium-low flame for about one and a half hour to low heat. At the end of cooking remove the vegetables leaving the broth on the fire and when it boils pour the Knödel still frozen and cook them for about 18 minutes.
If you already have some broth ready, just bring it to the boil and add the Knödel, wait 18 minutes and the goodness is served!
We recommend tasting them hot with the addition of freshly chopped chives.