1 leek, 600 grams of potatoes, 80 grams of grated Parmesan, 150 milliliters of cream or milk, salt to taste.
Remove the outer leaves of the leek and slice it roughly. Put it in warm water and add the coarsely chopped potatoes. Salt, cover with a lid and bring to a boil. The cooking time depends on the potatoes: when they are soft enough to be skewered, the leeks will be ready and so will the leeks. Approximately 25 minutes from the time the water boils. Once ready, drain directly into a jug and blend with an immersion blender. Once the desired density is obtained, add the cream or milk and the grated Parmesan. Blend again. If necessary, add salt or parmesan to obtain the desired flavor. Serve hot, alone or with croutons.