Clean the onion, garlic, carrots, leek and celery and cut into small pieces. Add the parsley and chop with a blender or cut very finely by hand.
Put the chopped, shredded vegetables and the remaining ingredients in a large bowl and mix together. Possibly add about 4 tablespoons of water.
Divide into portions of approx. 120 g each, shape into 16 meatballs and distribute on 2 baking trays with baking paper. Preheat the oven to 200 degrees circulating air. Fry the meatballs on one side for about 25 minutes. Then turn and fry for another 5 minutes.
For browning you can distribute the meatballs again on a grid and put them in the oven for about 5 minutes.