Wash and peel vegetables. Cut potatoes into small cubes, carrots into thin slices and leeks into thin rings. Cut zucchini in quarters lengthwise and then into thin slices.
For the meatballs peel onion and garlic and chop finely. Mix well meat, egg, bread crumbs, onion, garlic, parsley, oregano, salt, pepper and nutmeg and shape balls.
Bring soup to the boil. Add potatoes, carrots, 1 tsp. oil and bay leaf and simmer 6 minutes. Then add the meatballs and garlic and cook another 8 minutes. Add zucchini and continue cooking 3 minutes.
Serve stew sprinkled with basil.