Cut the leek into rings and fry in butter for 6-7 minutes. Peel the potatoes and cut into large cubes. Add the potatoes with the vegetable stock to the leek and cook. As soon as the potatoes are cooked, puree everything with the hand blender.
Put the soup back on the stove, add the whipped cream, gorgonzola, salt and pepper and stir well until the cheese has melted.