This recipe is made with leeks as a star ingredients so they are necessary and cannot be omitted. You could possible add a few celery stalks in place of part of the leeks but I haven't tried it. If you want to make potato soup without leeks, check out Slow Cooker Potato Soup, Stovetop Baked Potato Soup, Loaded Cheesy, Bacon, Corn, and Potato Chowder, or Loaded Cheesy Chicken Potato Chowder as excellent potato soup recipes.