Melt the butter in a deep pan, over a medium heat. Add the leek and cook without colour for about 5 minutes, stirring occasionally with a wooden spoon.
Add the chicken stock, turn the heat to high and bring to a boil, turn the heat down to low and simmer uncovered for about 20 minutes.
Add the potato, turn up the heat and bring back to a boil, reduce the heat to low and simmer uncovered until the potatoes are tender.
Season the soup with salt and sprinkle with chopped parsley when serving.
Keyword 4 ingredients, cheap easy meals on a budget, family dinner idea, healthy, potatoes