Wash and peel potatoes; Clean and peel the carrot; Peel the onions; Cut the potatoes, carrot and onion into small cubes; Peel and crush the garlic clove; Heat butter in a saucepan; sauté the prepared vegetables and garlic in it; Top up with the vegetable stock and cream, bring to the boil and simmer over medium heat for 15 minutes.
Wash radish leaves and pat dry; Cut 5 leaves into fine strips and keep them ready; finely chop the remaining leaves; Clean, wash and cut the radishes into fine strips; Cut off the cress leaves.
Finely puree the soup with the mixer; Add the cut radish leaves and half the amount of the cress leaves and purée finely again; season with salt, pepper and nutmeg.
Pour the soup into plates, garnish with the cut radish leaves, radish strips and the remaining cress and serve with roasted black bread cubes.