Cut the zucchini unpeeled into fine sticks. Steam the onion cubes in 1 tablespoon oil for about 15 minutes, then fill up with chicken stock. Puree the soup and season with curry powder and salt. Add the zucchini sticks and cook for 5 minutes. Dice the chicken breast, fry in the remaining heated oil in the pan and then add to the soup. Season the soup with cream and cress and serve.