Peel the potatoes, cut into large cubes and sauté in butter. Halve the leek, rinse, cut into pieces and add.
Pour the chicken stock and season with a little salt and pepper and nutmeg (freshly grated). Simmer gently for 20 minutes, add the whipped cream, bring to the boil and blend finely with a hand mixer.
Pass through a sieve, taste and refrigerate.
As a garnish, cut a small amount of raw leek into thin slices and roast in a frying pan.