Creamy Leek and Potato Soup

Let’s Talk Leeks!

New to cooking with leeks? Don’t be intimidated! Think of them as a BIG, but milder (also: delicious) green onion. The most complicated part of preparing leeks is washing them: Leeks grow in sandy soil, and often that sand gets trapped in between the leaves, so you want to rinse them very well. 

How to prepare leeks

Cut the darkest green edges off the top of each leek, and cut the root off the bottom. Slice the remaining leek (the white and light green pieces) in half lengthwise and place the flat side down on the cutting board. Slice the leek into thin slices. Full Tutorial: How to Cut Leeks

Now - the important part - place all the leek slices in a big bowl of cold water and stir the pieces around to shake all of the sand and dirt loose. Then, use your hands or a slotted spoon to remove the leeks from the water, leaving the dirt at the bottom of the bowl. (Don’t drain them by pouring through a colander - that just pours all the sand and dirt in the bottom of the bowl back onto the leeks!)

How much green should I trim off my leeks?

A lot of people recommend trimming the ENTIRE dark green portion of your leeks, leaving only the white and lightest green portion for recipes. But we typically like to use a bit more of the vegetable (why waste something if we don't have to, right?) The dark green parts of leeks are perfectly edible, but are often discarded in cooking because they can be a little bit tough or bitter (in quick recipes like our leek breakfast hash or leek frittata, for example, we prefer to use just the light parts of the leeks for a smoother, more buttery texture).

If you have a strong immersion blender (or a strong regular blender), it doesn't matter too much here that the dark green tops are a bit tougher, because we're cooking them in broth for a long time (and then blending them into a smooth purée). And in our testing, we really didn't notice any added bitterness from using the leek tops in this soup. If anything, the dark green pieces give it a better color and more complex flavor!

We trimmed off about half of the dark green pieces of each leek in this recipe - just cut off the very top half of the dark green area. So you're getting a bit of that bitter, complex flavor and gorgeous color, but we're still avoiding the ultra-tough, dry, leathery pieces at the very top.

All that to say: Trim your leeks however you want! We've included cup measurements in the recipe below; if you'd like to trim off the entire dark green part of each leek and use only the white and light green parts, feel free! You may just need an extra leek or two to ensure you have enough for this soup. (If you do prefer to trim all the dark green pieces, be sure to save them for adding to parmesan broth or turkey stock later!)

Our Basic Order of Operations

• Sauté leeks and garlic in a bit of olive oil until leeks are bright green and have softened slightly, then add potatoes and cook a few minutes more to get a bit of color on the veggies.
• Add salt, thyme, and vegetable stock to the soup, then bring it to a simmer over medium heat and cook until potatoes are tender (about 30-45 minutes).
• Purée with an immersion blender until nice and smooth. You can also purée this soup in a blender in batches (or skip blending all together and keep it chunky!)
• Stir in heavy cream, then do a final taste test and add salt and pepper as needed. 

Three rules for great soup

1. Add salt in layers. With any recipe, it's important to season a little at every step to ensure the flavors really pop! When the soup is blended, give it a taste and add additional salt a pinch at a time if the flavors don't quite pop yet (we use and recommend Diamond Crystal Kosher Salt).
2. Make sure the veggies are very soft before blending: A piece of potato should smush down fairly easily when you press it into the side of a pot with a spoon or spatula. This can take awhile - be patient! That squish-ability is the key to a smooth, silky soup.
3. Use a good immersion blender. A great blender is key to a smooth soup here. (Pro tip: Always make sure the head of your immersion blender is completely submerged in the soup while blending to prevent spatters and burns.) If your immersion blender doesn't always get things as creamy as you'd like, you may want to use a powerful countertop blender instead. For the creamiest soup, keep blending for a minute or two even after the soup is mostly puréed! A good blender or immersion blender should give you a very smooth soup, but if you'd like an even silkier consistency you can strain the finished soup through a mesh sieve or run it through a food mill. 

Riffs and Substitutions

• For a vegan soup, replace the heavy cream with additional vegetable stock or use coconut milk (this recipe is also great with a scoop of our Magic Cauliflower Cream sauce instead of heavy cream!)
• Add a splash of white wine
• Swap some or all of the potatoes for cauliflower florets if you prefer! They'll give you a very similar texture here.
• Add some protein (and some texture!) by topping this soup with some crispy bacon, pancetta, or prosciutto.  
• Leave it chunky! If you’re not a fan of cream-of-something style soups, skip the blending step and leave the veggies whole for a rustic stew. If you go this route, we recommend dicing the potatoes and leeks into smaller pieces (about ¼ inch) so it's easier to eat.
• Play with the garnishes! Top this soup with a bit of fresh thyme, a drizzle of heavy cream or crème fraîche, a few croutons, or some pepitas (pumpkin seeds).
• Simmer a bay leaf with the soup ingredients for some extra depth of flavor (just remember to remove it before you blend the soup!)