Onions peel and cut into slices. Clean, wash and cut the leek into rings. Clean, wash and slice the carrots. Clean, wash and cut kohlrabi into sticks.
Wash, clean and slice the tomatoes. Heat oil in a pot, fry onions in it, add leek, fry briefly. Add half of the tomatoes and tomato paste, fry briefly. Deglaze with broth, bring to the boil.
Add the kohlrabi and carrots, bring to the boil again and cook covered over medium heat for 12-14 minutes. Meanwhile wash basil, dab dry and cut the leaves into strips. Season stew with salt, pepper and sugar, add remaining tomatoes and basil strips.
Serve stew garnished with basil.