Divide cauliflower into florets. Peel potato and cut into small cubes. Peel and chop onion. Heat oil in a pan and sauté the cauliflower, potato and the onion while stirring. Pour in broth, bring to a boil and cook for about 20 minutes. Then puree, stir in the cream and creme fraiche, heat briefly and season with salt, pepper and nutmeg. Cut leek into slices and blanch briefly in boiling water. Cut the ham into small cubes.
Distribute soup among bowls, garnish with leek slices and ham cubes and serve sprinkled with dill.