Boxed vegetable broth comes in a wide variety of colors and flavors; if you want a whiter potato soup, look for one of the clear, light broths, not the carrot-heavy orange versions. Pureeing the soup right in the pot with an immersion blender keeps it rustic; do it in a regular blender and it will be silkier and a little more elegant. The regular blender can also make the soup a little pasty because it smashes the potato starch so thoroughly.