Clean the leek and cut into fine rings. Sauté in hot oil and deglaze with wine and stock. Pour in the cream and simmer covered for approx. 5 minutes. Then puree very finely together with the butter in a blender. Season to taste with salt and cayenne pepper.
Season the milk with salt and nutmeg, bring to the boil and season with the truffle oil. Beat the milk with a hand blender or milk frother.
Distribute the soup in cups (the double-walled glass cups are very suitable). Skim off the milk foam and carefully pour it onto the soup. Froth the milk again and again in between.