Peel the potatoes and cut into bite-sized pieces. Wash the leek and cut into rings.
Fry the potato pieces and leek in a saucepan with very little butter for 2 minutes, then add the stock. Simmer for a quarter of an hour until the potatoes are tender.
In the meantime, cut the gorgonzola into small pieces and add to the soup, simmer until dissolved. Season well with the spices.
Ciabatta or baguette goes well with it.
If you make the soup as a pre-soup, the amount given is enough for about 6 people.