Bring 1/4 litre of water to the boil, dissolve the broth in it, let it cool down. Wash and clean the cucumber. Put a piece (about 6 cm) aside. Peel the rest of the cucumber, cut it roughly into pieces and puree. Mix cucumber, stock, lemon juice, yoghurt and sour cream.
Season to taste with salt, pepper and nutmeg. Chill cucumber soup for at least 30 minutes. Cut the rest of the cucumber into thin slices. Wash the dill, dab dry and, except for a few dill flags for garnishing, chop finely and stir into the soup. Arrange soup in bowls and garnish with cucumber slices and dill