Wash and dry the green beans and cut them into bite-sized pieces. Peel the potatoes and finely chop them. Peel and finely chop the onions.
For the roux, melt butter, sweat onion in it, dust with flour and roast, then deglaze with vinegar and pour in vegetable soup.
Add green beans and potatoes to the soup and cook until soft.
Meanwhile, wash, dry and finely chop the parsley and dill.
Mix in the herbs and puree with a hand blender. Thicken with sour cream and season with salt and pepper to taste.
Before serving, sprinkle a few more herbs on top.
The soup can also be made a little more substantial with Frankfurter or Debreziner sausages.