The Food Lab: How to Make Potato Leek Soup the Easy and Easier way

The Food Lab

Unraveling the mysteries of home cooking through science.

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The easy, easier, and easiest ways to make a luxuriously creamy potato-leek soup. [Photographs: J. Kenji Lopez-Alt]

Get the Recipe

Today I'm going to show you how to make two different versions of the same dish. They both use the exact same ingredients to produce similar end results. The first recipe for potato leek soup is the most involved, and it'll make just about the tastiest potato leek soup you've ever had. Light, creamy, packed with flavor, and soul-satisfyingly delicious. The second takes a fraction of the time and produces a soup with very similar flavor, but a slightly inferior texture. It's still something I'd happily serve to dinner guests any night of the week.

Think of it as an example of my 20/80 rule of cooking in action: if you can make a streamlined version of a dish that's at least 80% as good as the original with less than 20% of the effort, then you are perfectly justified in doing so from time to time.

But first, a quick story.

I never intended for a casual comment to haunt me for the rest of my life, but it looks like that's just how it's going to be. It all started innocently enough. My not-then-wife Adri and I were dining out at a fancy-pants French restaurant. I'm not the best conversationalist in the world, but these were also back in the days when silences were just uncomfortable enough that I'd feel compelled to make a comment on whatever was happening at the moment. It was a dangerous impulse.

"They used a blender to make this soup," I said matter-of-factly about the potato and leek soup we were enjoying as our first course.

"How do you know that?" she asked.

"Because you can taste the glue-iness in the texture. See how it's a little sticky and gooey on your tongue? That's because when you blend potatoes, it causes swollen starch granules to burst, which makes the whole thing sticky, like melted cheese or dough."

I honestly don't know why she married a guy who says things like this during a romantic night at a fancy restaurant.

"If you want really light, smooth potato soup," I continued, "you need to press your potatoes through a tamis, you can't just stick 'em in the blender"

"Oh yeah, you're right. It is sticky," she said as she nudged the bowl away from herself ever so slightly. "Now that I notice it, I'm not sure I like it any more." I could see the look in her eyes. That one that says welp, there's yet another dish I used to love that Kenji's ruined for me.

I immediately regretted saying it. This was the beginning of the end. Now that she'd cottoned to the idea that gluey potato soup = improper potato soup, I knew that from that day forward, I'd never get away with cheating at potato soup again. It's something that I'd done many times in the past with nary a complaint from anyone other than my own conscience, but no more.

In fact, you'll find that the vast majority of potato soup recipes out there use a blender. Some recommend that you keep blending to a minimum in order to improve the texture, while others use a very low proportion of potatoes to liquid to keep things looser, but the fact remains that no matter how few potatoes you use and no matter how briefly you pulse, any degree of blending will turn a potato soup gluier than no blending at all.

See, while what I said was perfectly correct—you can very easily tell whether a potato soup was made the quick and easy way or the elbow-grease and patience way—truth be told, I don't actually mind the texture of blended potato soup. In fact, there are times when I crave it: I kinda like how it coats your throat and gives you a rich, almost cheese-like impression.** But still, if light and creamy is what you're after, then potatoes-in-the-blender is not the way to get there.

**A trait that I take full advantage of when making my gooey 100% vegan cheese sauce.

Potato-Leek Soup, v1.0: The Full Effort

Even at it's most difficult, potato-leek soup is pretty darn easy to make. It requires only a few ingredients— leeks, butter, potatoes, broth, cream, and some aromatics—and some very simple knife skills and cooking techniques.

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I start mine the classic way, with leeks slowly cooked down in butter. Leeks have a very mild onion flavor with very little of the sweetness that bulb-style onions have, which helps them blend into the background in any soup. There's a reason they're known as the soup onion.

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The trick here is to slowly cook the leeks without letting them (or more importantly, the butter) get any color on them. This jump-starts the softening process, which can actually take a fair bit of time if you just try and boil leeks in broth.

I've seen some recipes that call for adding the potatoes to the softened leeks and giving them a sweat in the butter before adding any kind of liquid, but I haven't found any advantage either flavor-wise or texturally to warrant doing so. As soon as my leeks are soft, I add potatoes cut into large chunks. Big chunks are important for this method, as we're going to be fishing them out before blending later on. Starchy russets that fall apart as you cook them give potato soup the cleanest, lightest texture.

Next I add just enough homemade or store-bought low-sodium chicken stock to cover, a couple bay leaves, and a big grinding of black pepper. I bring it to a simmer and cook until the potatoes are fall-apart tender.

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There's a dish from Adri's native Colombia that's wildly popular in Bogotá called Ajiaco (check out my recipe here) which uses a particular type of potato that breaks down on its own as it cooks, thickening the soup without any need for additional blending or mashing.

We're not so lucky in North America. To get a really nice smooth texture out of potatoes without any of the pastiness associated with blending, we have to mash them separately. At a fancy restaurant, that means painstakingly pushing the cooked potatoes through a flat, fine-mesh strainer called a tamis. At home, I just use a potato ricer, fishing out the cooked potatoes and ricing them into a separate bowl before blending the remaining broth with the leeks and a splash of dairy, then whisking everything back together to serve.

For that dairy element, many traditional recipes call for cream or milk. I find that a combination of cream and buttermilk, with its creamy texture and light acidity actually makes for a brighter, tastier soup, while a shave of nutmeg gives it a little more character. Go through this whole process, sprinkle the bowl with some black pepper and some minced chives or scallions, and you'll have just about the tastiest bowl of potato-leek soup you've ever had.

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Feeling a little lazy? I don't blame you. Read on.

Potato-Leek Soup v2.0

This version is almost identical to the full-blown version, with the exception that rather than pressing the potatoes through a ricer, you just dump all of the ingredients into a blender, blending it just until puréed (the more you blend it the gluier it becomes).

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For an extra-smooth soup, press it through a chinois or a fine mesh strainer using the bottom of a ladle.

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Sure, it's the gluier than its pressed brother, but as I said, sometimes that really doesn't bother me. Is it something I'd serve in a fancy-pants restaurant? No way. But it's a soup I'm more than happy to enjoy at home. At least when Adri is away, that is.

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