The Right Way to Cut a Leek, According to Martha

A fan of their sweet and delicate flavor, leeks are Martha's favorite allium. These long green members of the onion family are widely available but can also be slightly intimidating. Their many layers hide a lot of dirt that will ruin any dish if not properly removed. Cleaning and cutting leeks might be a slightly tedious task (some might say meditative!) but not a difficult one. And luckily, you need little more than a sharp chef's knife to cut a leek.    

What Are Leeks?

One of the more overlooked members of the allium family, the versatile leek has a distinctive appearance and flavor—it looks like a giant green onion but is sweeter and milder. Alliums are technically not vegetables, but even if you haven’t heard of this distinctive subgroup of plants, you’ve definitely cooked with them. Leeks, onions, scallions, chives, and even garlic fall within this family. Alliums are unique: they are ingredients that can melt and disappear into any given dish but just as easily stand out as the star of the show.

Choosing Leeks

When shopping for leeks, keep two main criteria in mind: their color and size, says Richard LaMarita, chef-instructor of Plant-Based Culinary Arts at the Institute of Culinary Education’s NYC campus. “The edible part is the sheath of leaves often mistakenly considered the stem or stalk,” he says, adding that the leaves should not be cracked, wilted, yellowed, or browned in any way. 

The leeks themselves should be tight and compact. LaMarita says this indicates “the leaves underneath will be more tender and light green, giving you more leek to work with. In a ripe leek, the white part will be about three inches long up the shaft.” Lastly, he recommends avoiding very thick leeks, which are more fibrous and tougher to eat. 

How to Cut a Leek, Step by Step

Before you begin to cut your leeks, prepare your workstation. Be sure you're properly equipped with a large cutting board that won't slide around on your countertop and a sharp chef's knife that will help cut through all the layers. 

Trim the Tops 

Understanding the anatomy of a leek is the next step in cooking it to perfection. LaMarita stresses an often misunderstood fact about the leek is that it’s entirely edible! He suggests cutting off only the top 2 inches of dark green leaves—otherwise, the whole leek is edible depending on your intended use. "Understand the most delicate part starts at the base, the white part,” he says. “Next is the light green, and finally, the darker green leaves on top—after you have cut off the top few inches."

Trim the Root 

This part of the process is often where people make a crucial mistake. Be sure to cut just where the root starts. As Martha points out, cutting too far up the leek will cause the leaves to separate and the leek to fall apart, making it more challenging to cut the leek into other shapes.

From this step, "there are basically two methods to properly clean leeks," LaMarita says. And the way you clean them depends on the way you cut them, now that they are trimmed. 

Either Cut Lengthwise for Cleaning

Using a sharp chef's knife, LaMarita says to “cut the leek lengthwise, keeping the base or core intact and then gently opening the leek from the top and kind of fanning them out." From there, since the leaves are still attached to the core, you are able to wash each layer well, under cold running water. 

Or Cut Into Rings for Cleaning 

For this method, do not cut your leek in half lengthwise; simply cut the leek into 1/2-inch rings crosswise. This yields a typical method of preparation in most recipes. "Place the cuttings in a large bowl and give the prepped leek a triple bath, swishing your hand through the cuts and pouring off the water." says LaMarita. Three times is the minimum for washing, he says. If you use this method, be sure to give the final batch of water and sediment time to settle, and use your hands or a spider tool to lift the leeks out of the water rather than risk pouring the sediment back into the leeks.

Other Ways to Cut Leeks 

Dice: Once your leeks have been cut in halves lengthwise, you can cut each half in half again (resulting in four quarters). Then, cut crosswise for a dice, a common cut that is useful in everything from stir-fries to soups, particularly if you're looking for the leek to soften significantly and almost disappear.

Half moons: Leeks cut into half moons are similarly useful to a dice in that they are good for a variety of dishes, but they’re slightly larger pieces that will have a larger visual presence in most dishes. Take a halved leek and cut each half crosswise into 1/2-inch slices to yield attractive half-moon or semicircular shapes.  

Julienne: To julienne your leek, which is a method of cutting that results in thin strips, simply take a halved leek and cut each half crosswise into 3-inch sections. Working with one section at a time, finely slice it parallel to the direction of the leaves to end up with thin strips. These will curl when briefly soaked in ice water for an attractive garnish, or they will fry up nicely in some hot oil for a crunchy topping. 

Cooking With Leeks 

Knowing the entire leek is edible widens the breadth of recipes and uses where the leek can shine. "The light and darker green leaves do cook well and can be added to scalloped potatoes or a stew," says LaMarita. "They will take longer to cook than the tender white parts. The farther up the leek you go, the tougher the leaves, but with patience, these leaves can be cooked."

Otherwise, since leeks are in the allium family along with onions, they can be a direct substitution in many cases—provided they are cleaned properly. Keep in mind that their flavor is much more mild than that of onions. "Cut small, they make a great substitute for onions," La Marita says. "Their flavor is excellent. They are delicious braised and served with the reduced braising liquid of maybe chicken stock mixed with white wine and aromatics. They are also delicious in a creamed scalloped potato dish. I would not hesitate to use them in a stew or soup."