Potato Leek Soup is arguably the one soup that every aspiring cook should have in their repertoire. Also called “Potage Parmentier,” it is the first soup featured in Julia Child’s iconic book, Mastering the Art of French Cooking. In fact, it is the very first recipe of any kind in the book, and I believe it holds this place of honor for very good reasons. First, it is incredibly simple to make, having only four ingredients (five if you include water) and requiring only the most basic of kitchen equipment. Second, despite its simplicity it is very tasty comfort food. Just think of it as mashed potatoes in soup form. Lastly, and perhaps most importantly, it is the start of many other recipes, each with its own distinctive flavor.
I used to think of Potato Leek Soup as a blank canvas, but now I consider it more like the culinary version of a “little black dress”: it’s simple and elegant by itself, easy to accessorize, matches everything, and works for nearly any occasion. But unlike the dress, potato leek soup is gender-neutral and completely edible.
If simplicity, good flavor, and creative inspiration aren’t enough, there’s another benefit: this soup is really easy on the tummy. Years ago I developed advanced symptoms of undiagnosed Celiac disease. I won’t go into the gory details; suffice it to say I was ill for days and in constant stomach pain. I literally lived on this soup for a week because it was the only thing I could keep down. I have suggested this recipe to people with ulcers and other digestive issues that affected what they could eat, and so far no one has said it caused them any trouble. It’s not a cure for anything, but comfort food is important when you are suffering.
You can use onions in this soup instead of leeks, but leeks have a milder flavor that won’t overpower the milder potato. If you decide to use onion, reduce the amount slightly. If you decide to stay with the more classic leeks, then you’ll need to clean them out first. Leeks shoot up through the soil as they grow, trapping grit in between their layers. No one likes grit in their potato soup, but fortunately it is very easy to avoid. Simply slice off the bottom half inch or so, and cut off the dark green part at the top. Now slice the leek in half length-wise. The layers easily separate, and all you have to do is run cold water over the leek, and pull the layers apart slightly to let the water run between them. After that you can slice the leeks into half inch sections.
As I mentioned previously, this soup is very easy to make. All you need to do is remember 4-3-2-1: 4 cups of chopped potatoes, 3 cups of chopped leeks, 2 quarts of water, and 1 tablespoon of salt. Add the potatoes, leeks and salt to the water. Bring it all to a boil, then reduce it to simmer partially covered for about 45 minutes. Remove from heat and blend using a immersion blender. You can use a regular stand-up blender if that is all you have, but do it in small batches. After blending, you can add a little butter or heavy cream. That’s all there is to it!
Of course, there are a lot of ways to jazz it up. You can add some chopped fresh herbs, parsley and tarragon being favorites of mine. You can also use vegetable or chicken broth in place of water, but I really don’t find it necessary. Some dried spices are nice as well, and cumin tops the list for me. But don’t use too much or it will dominate all the other flavors. Watercress is a variation that Julia Child mentions in her book – just chop up a handful and add it five minutes before blending. Lastly, you can add about half a cup or so of whipping cream at the end, chill it, and voila: you have just made vichyssoise!