To understand how potatoes behave in the stock pot, Katherine puts a favorite soup under the microscope – literally.

Potato leek soup is the perfect soup. It is heaven pulled from the ground in all its humble grassy beauty. Potato leek soup is good-looking, simple, and flexible. It can be made vegan and provides nutrients and fiber with few calories. It is cheap, scales up for a crowd, and freezes well. Plus you have to love a soup with more names than ingredients. As a comforting wintertime staple, we call it what it is – potato leek soup. In tiny cups, sprinkled with chopped parsley and freshly ground black pepper, it becomes potage Parmentier, a rich tasting but delicate entrée to an elegant dinner party * . Chilled, with fresh cream, it is Vichyssoise, the cool, light partner of a good baguette and a glass of Pouilly-Fumé on the patio in summer. And my mother-in-law has demonstrated many times that when the holidays overwhelm your fridge, you can store a huge pot of potato leek soup on the porch overnight – as long as you put a brick on the lid to keep the raccoons out.

This amazing soup is the just about easiest thing in the world to make. Julia Child’s version is probably the most widely used, and the one I like: simmer equal parts cubed potato and sliced leek in water until they are tender. Add salt to taste and puree. A bit of cream is optional. A dusting of chopped parsley and freshly ground black pepper is divine. I like to err on the side of more potatoes than leeks, but the soup is robust to variations in proportion.

But is it really so easy? If you trust the internet more than you trust your favorite dog-eared chocolate-spattered cookbook with the broken spine and decades of marginalia (silly you), you may worry that without the right kind of potato and extremely careful handling, your soup will end up gluey. Is any wallpaper not pre-pasted these days? Doubtful, but everyone seems to describe gluey potato soup or mashed potatoes as “wallpaper paste.” I will say right up front that gluey soup has never happened to me, but given all the stress over this utterly simple soup, it seemed worth investigating. Continue reading →